DIVISION OF REPTILES INTO ORDERS - Of the various modifications that have been proposed in the classification of Reptiles the more important are mentioned in the historical part of this article. We adopt here a serial arrangement of those orders which seem to be well established, having already referred to tha attempts that have been made to arrange these orders into higher groups.

Order 1. ICIITHYOPTERYGIA (extinct). Marine Reptiles with a Cetacean-like naked body and with four limbs formed into paddles, the parts of which after the humerus are not differentiated as to form or function. Tail long. Vertebrm numerous, biconcave ; no sacrum. Dorsal vertebrx with double tubercles ; ribs movable, the anterior with bifurcate heads. Head large, with long powerful snout, joined to the trunk without neck. Quadrate bone immovably articulated to squamosal. A foramen parietale is present. Orbits -very large with a circle of sclerotic plates. A pair of clavicles rest upon an interclavicle and pass laterally to the scapulm ; a pair of broad not over-lapping coracoids form the posterior part of the pectoral arch. A sternum is replaced by a series of abdominal splints.

Fam. a. Sattranodontidte. Edentulous. Genus : Sauranodon, from the Jurassic formations of the Rocky Mountain region.

Fam. b. Ichthyosauridw. Teeth numerous, implanted in a com-mon alveolar groove. Genus: Ichthyosaurus, from Mesozoic strata up to the Chalk.

Order 2. ANOMODONTIA. (extinct). Lacertiforno Reptiles, the skull and four limbs of which are Lacertilian in most of their characters. Vertebrm biconcave, four or five of them anchylosed together and forming a sacruin. The tubercular and capitular articulations are separated, the former and longer being on the diapophysis, the latter and shorter on the centrum ; ribs movable, the anterior with a bifurcate head. Os quadratum suturally connected with the skull. A foramen parietale is present. Jaws Chelonian and probably cased in horny sheaths ; either edentulous or each maxillary bone was armed with a long overgrowing tusk, which sometimes was accompanied by other smaller teeth. The pectoral arch consisted of scapula and coracoid, but a clavicle seems to have been absent. Pelvis very strong, with continuous ischio-puhic symphysis.

Genera : Dicynodon, Galcsaurus.

Order 3. DINOSAIIRIA (extinct). This comprises Reptiles of a great diversity of form and size, some adapted for a terrestrial, others for an aquatic life, some carnivorous, the majority herbivorous, but all distinguished by charac-ters leading more or less closely from the Reptilian up to the Avian type. The majority of trunk vertebrm have flat or slightly concave articular ends, sometimes a few of the anterior are convex in front ; cervical vertebrm numer-ous ; a sacrum is formed by more than two coalesced vertebrm. Neural arches united to the centra by sutures. Thoracic ribs movable, with a bifurcate head ; cervical ribs united to the vertebrm either by suture or anchylosed.

Os quadratum suturally connected with the skull. The premaxillary bones are separate, and the rami of the lower jaw united in front by cartilage only. Form of the teeth variable; they are not anchylosed to the bone. Two pairs of limbs are present, of which the hinder pair is the longer and larger, and generally atnimlatory. The struc-ture of the pelvis and hind limbs partly Ornithic ; the pelvic bones arc not coalesced with each other or with the sacrum ; the pubis enters into the forination of the ace-tabulum, and the ilium is prolonged forwards in front of the acetabulum ; ischia united in a, median ventral symphysis. The head of the femur is placed at a right angle to the condyles; tibia with a procnemial crest, a,nd a ridge for the fibula, which is complete. The proximal row of tarsals is formed by the astragalus and calcaneum only, and the former sometimes anchylosed with the tibia, thus forming the upper portion of the ankle-joint.' Order 4. ORNITHOSAIIRIA. (extinct). Reptiles with the fore limb adapted to support a flying membrane, and with the remainder of the skeleton secondarily modified for aerial progression. Vertebrn not numerous, proud-ous ; from three to six forming a sacrum ; cervical vertebrio exceeding in sizo the others. No neuro-central suture. Anterior ribs with bifurcate heads. Skull large, bird-like, with long ja,ws. Os quaclratum suturally con-nected with the skull. Orbits very large, with a ring of sclerotic plates. Sternum broad, completely ossified, with a median crest anteriorly. Scapula and coracoid slender, Bird-like ; no clavicle. Phalanges of the ulnar digit exceedingly elongate. Pelvis weak ; hind limb smaller than fore limb. Bones generally hollow, many with pneumatic foramina.

Fam. a. Plerosauria. Jaws toothed ; scapula and coracoid separate. Genem: Pterodaetylus, Rhamphorhynehus, Dimorphodon, from Jurassic formations of Europe ; of small or moderate size.

Fam. b. Pteranodontia. Edentulous ; scapula and coracoid solidly united, the former articulating with the common neural spine of the vertebrm. Genus: .Pteranoclon, from Cretaceous strata of Kansas ; specimens with a spread of wing of some 20 feet.

Order 5. CROCODILIA. Reptiles with Lizard-like body, and long powerful tail adapted for swimming. Limbs short, especially the -anterior ; five digits in manus and four in pes; only three of the digits are clawed. A dermal armour, consisting of flattened bony scutes, covers the back, and in some genera the abdomen. Teeth in a single row, implanted in distinct sockets. Nostrils generally at or near the end of the snout. Vertebrm with the neuro-central suture persistent. Two sacral vertebrm only. The majority of the cervical and trunk ribs double-headed, attached to the diapophysis and centrum of the vcrtebrai. From seven to nine of the anterior dorsal ribs are united with the sternum by sternal ribs. Bones of the skull very solid, firmly united by sutures, as is also the quadrate bone. Heart with a double ventricle. Copulatory organ single, situated in the cloaca.

Fam. a. (or suborder) Proccelia. With proccelous vertebrx. All living genera and the extinct forms down to the Chalk belong to this division.

Fam. b. (or subordcr).Anzpliiece/ia. With amphiccelous vertebrx. All the genera are pre-Cretaceous : Teleosaurus, Goniopholis, Strep-tospendylus, Steganolepis, Galesaurus (?), Belodon.

Order 6. SAIIROPTERYGIA (extinct). Marine Reptiles with long neck, small head, long tail, natatory limbs, and a naked skin. Hind and fore limbs identical in structure and form, transformed into Cetacean-like,,paddles with five digits, which were composed of numerous phalanges and enclosed in a, common skin. Teeth in a single row in both jaws, implanted in distinct sockets. Vertebrm amphicceb ous, with the neuro-central suture persistent ; single, headed ribs are attached to the long diapophyses of the dorsal vertebrm. Sacral vertebrm two. Quadrate bone suturally united with the skull. A parietal foramen. No sclerotic ring. Neither sternal ribs nor sternum are

These characters may not fully apply to all the genera which have been referred to this order, as some are known from their skulls or other fragments only-.

The best known are the PLESIOSAURIANS (q.v.) proper : - Neusti-cosaurus, from the Trias, with paddles in front and ordinary limbs behind ; gigantic forms from the Trias, as Nothosaurus, Simo-saurus, .Pistosanrus, or post-Triassic, as P/esiosaicrus, and Pilo-saurus, Polycotylus, and .Elasmosaurus (or Diseosaurus) from the Lias and Chalk.' Order 7. RHYNCHOCEPHALIA. Lacertiform Reptiles, with four limbs. Vertebrm with flat ends ; two in the sacrum ; the tubercular and articular surfaces are united ; ribs single-headed. Os quadratum suturally united with the skull and pterygoid; an osseous infra-temporal bar. Foramen parietale present. Sternum and a, system of abdominal ribs well developed. Copulatory organs absent ; urinary bladder present.

One recent genus : Hatteria. Represented in the Upper Cretaceous and Lower Eocene by Champsosaurus, in the Trias by Phyneho-saurus, Hyperodapedon, and in the Permian by Proterosaurus, Sphenosaurus, Telerpeton.(?), Saurosternum (?).

Order B. LACERTILIA. Lizards. Vertebrm generally proccelous, with short or rudimentary transverse processes; sacral vertebrm not exceeding two ; ribs single-headed. Os quadratum articulated with the skull. Parts of the ali-and orbito-sphenoid regions fibro-cartilaginous. Temporal region without, or with only- one, osseous bar. Limbs four, two, or absent ; when they are present, a sternum with sternal ribs and a pelvis are developed. Copulatory organs paired ; urinary bladder present. Integuments with horny or sometimes bony scutes.

For the numerous recent genera see LIZARDS. Distingui,hable representatives of the order appear first in Jurassic formations and thence downward to our period : Acrosaurus, Ardeosaurus, Pleura-saurus, Saphiosaurus, Ateposaurus, and IIonweosaurus from the Oolite; Kuthetes, Saurillus, Macellodon from the Wealden ; Dolieho-saurus, .Aeleosaurus, Coniosaurus, laaphiosaurus from the Chalk. From Tertiary formations in-Europe numerous small remains are known, whilst those described from Australia belonged to nmeh larger forms, showing more or less affinities to the Lizards of the present Australian fauna.

A distinct division of this order includes tbe extinct Mosasaurians, which are, in fact, the Pinnipedes among Lacertilians. Their limbs, of which they had two pairs, are transformed into paddles; by their long Snake-like body and large size the marine Reptiles form the nearest approach in nature to the modern creature of imagination, the " Sea-Snake." There is no question that they deviate more from the Lacertilian type than any of the other fossil forms mentioned above, especially in some of their cranial characters, which are more Ophidian. Hence Cope placed them into a distinct order of Reptiles, Pythonomorpita. Their body was covered with osseous scutes.

Besides Mosasaurus, remains of which have been known and. described since the year 1766, a number of other genera from Cretaceous rocks of Europe and North America have -been distin-guished by Owen, Cope, Marsh, ancbDollo : Liodou Clidastes (fig. 2), Sixonectes, Plateearpus, Baptosaurus, Liplotomolon, Eclestosaurus, Ifolosaurus, Lestosaurus, Tylosaurus, Ptcrycollasauras, Plioplak-carpus.

Order 9. OPHIDIA. Snakes. Vertebrx proccelous, extremely numerous ; no sacrum ; ribs single-beaded. No chevron bones on any of the vertebrm. Not only the quadrate bone is movably articulated to the skull, but also the suspensorium and the bones of the palatal maxillary apparatus are movable ; brain capsule entirely osseous. No quadrato-jugal arch. No foramen parietale. Rami of the mandible united by ligament. No trace of anterior extremities, and posterior only sometimes rudi-mentally indicated. Copulatory organs paired ; urinary bladder absent. Integuments folded into regularly ar-ranged scales.

For the numerous recent genera see SNAKES. Fossil forms are scarce, and do not appear before the Eocene (Laaphis, Palesophis, Paleryx).

Order 10. CHELONIA. Tortoises and Turtles. Cervical and dorsal vertebrae not numerous. The dorsal vertebro and expanded ribs (with tho exception of Sphargis) are united into a carapace, the elements of which are immov-able, and which is completed ventrally by a number of dermal bones, a true sternum being absent and replaced by a plastron. All the bones of the skull are suturally united, with the exception of the mandible and hyoid; the dentary portion of the mandible consists of one bone only. Pectoral arch consisting of the scapula, with which the precoracoid is united, and the coracoid. Clavicles aro represented by the anterior elements of the plastron. The pelvis consists of the usual bones, but is not attached to a sacrum. Two pairs of limbs. No teeth, these being replaced by horny sheaths of the jaws. Copulatory organ single. Integuments consisting of horny scutes covering the carapace, and. of scales and tubercles on the soft parts.

For the numerous living genera see TORTOISES. Remains of extinct 'Tortoises are found from the Tries downwards, but they do not show any approximation to some other Reptilian type, or indicate a, successive development The most generalized type, Sphargis, is not older (according to present evidence) than some of the more specialized genera, its earliest representative being the remarkable Protostega from North-American Cretacean formations. Some of the Tertiary fossils exceeded. in size the largest of living forms, such as the Himalayan Colossochcks, the GermanNacrochelys, the North-American Atlantockelys. (A. C. G.)