212 KEPTILIA 



lateral ones triangulär, and antorbital opening long and narrow. External 

 nares small ; interclavicle blade-like ; dorsal scutes coarsely sculptured. Elgin 

 Trias; Scotland. 



Sub-Order 3. MESOSUCHIA. Huxley.i 



Snoiit greatly elongated in the earlier forms, short and hroad in some of the later. 

 External nares unpaired and terminal ; internal nares confluent, opening at posterior 

 margin of the secondary palate formed hy plates of the maxillae and palatines, there 

 heing no outgrowths from the pterygoids. Eustachian passages open grooves on the 

 hasisphenoid. Parietal and frontal unpaired. Vertebrae amphicoelous, or more 

 rarely amphiplatyan. Clavicular elements wanting. Coracoid elongated, with slight 

 perfm^ation. Pubis excluded from acetabulum, and borne on an anterior process of the 

 ischium. Anterior extremities pentadadylate ; fifth digit of pes rudimentary. 



The Mesosuchia, which comprise all the Jurassic and a few Lower Creta- 

 ceous crocodiles, were separated by Huxley from the later Eusuchia chiefly on 

 account of differences in the palate, eustachian passages, and vertebral centra. 

 In the present group the pterygoids do not develop secondary plates to 

 prolong the canal of the nares, which opens at the hinder margin of the 

 palatines ; the eustachian canals are not closed ; and the vertebrae in all but 

 the latest forms are amphicoelous. Like the typical Cretaceous and modern 

 families, the Mesosuchia comprise both long-snouted and broad-snouted croco- 

 diles, the latter, however, not appearing until the Purbeckian. All except the 

 latest forms are adapted for an exclusively aquatic life, and are known from 

 Europe,,Madagascar, Patagonia, and perhaps North America. 



Section 1. LoNGiROSTRES. Lydekker. 



Snout greatly p'oduced. Nasals, as a rule, not reaching the premaxillae and 

 external iwstril. Mandibular rami united in a long Symphysis formed by the dentary 

 and splenial. Vertebrae amphicoelous. 



Family 1. Teleosauridae. Zittel. 



Teeth conical, slender, closely set. Orbits entirely enclosed, superioriy or more 

 rarely laterally directed, and notably smaller than the subrectangular supratemporal 

 vacuities. Prefrontals small, lachrymals well developed. Antorbital mcuities small, 

 laterally placed. Anterior limb only about half as long as the hinder pair. Dorsal 

 armour consisting of a paired series of broad, overlapping plates; ventral plates 

 suturally united, forming several more or less irregulär series, or a mosaic of small 

 polygonal scutes. Jura. 



^ Literature : 



d' Alton, M., Sind Burmeister, IL, Der fossile Gaviale vou Boll, Halle, 1854. — Bronn, H. G., 

 aud Kaup, J. J., Ueber die gavialartigen Reptilien der Liasformation. Stuttgart, 1841. — Dollo, L., 

 Premiere note sur les Crocodiliens de Bernissart (Bull. Mus. Roy. d'Hist. Nat. Belg. vol. II. p. 309), 

 1883. — Deslangchamps, E. E., Notes paleontologiques. Caen and Paris, 1863-69. — Le Jura Nor- 

 mand. Caen and Paris, 1877-78. — Deslongchamps, J. A. E., Memoir sur les Teleosauriens de 

 l'epoque jurassique (Mem. Soc. Linn. Norm. vol. XIII.), 1863. — Fraas, E., Die Meerkrokodile 

 (Württ. naturw. Jahresh., vol. LYII. p. 409), 1901.— Palaeontogr. vol. XLIX. pp. 1-72, 1902.— 

 Ilulke, .T. W., Skeletal Anatoniy of the Mesosuchia (Proc. Zool. Soc. London, pt. 4), 1888. — 

 Koken, E., Thoracosaurus macrorhynchus BL, aus der Tuffkreide von Maestricht (Zeitschr. deutsch. 

 geol. Ges. vol. XL. p. 754), 1888. — hortet, L., Les Reptiles fossiles du Bassin du Rhone (Arch. 

 Mus. d'Hist. Nat. Lyon, vol. V.), 1892. — Sauvage, E., Memoir sur les Dinosaurs et les Crocodiliens 

 des terrains jurassiques de Boulogne-sur-Mer (Mem. Soc. Geol. France [2], vol. X.), 1874. — Winckler, 

 T. C, Etüde sur le genre Mystriosaurus (Arch. Mus. Tylere, vol. IV. pt. 1), 1876. 



