428 PROF; T. H. HUXLEY ON STAGONOLEPIS ROBERTSONI, 



The ischium is more elongated dorso-ventrally, and is shorter 

 antero-posteriorly, than in the Parasuchia. Its acetabular margin 

 is excavated by a deep notch, which marks off a stout pubic process, 

 as in the next suborder. 



The manus and pes are constructed as in the next suborder*. 

 There are two longitudinal series of dorsal scutes, some of which 

 are longitudinally carinated ; and in most, if not all, of the members 

 of this suborder there is a ventral thoraco-abdominal shield com- 

 posed of not more than eight longitudinal series of undivided flat 

 scutes. 



Genera. JSteneosaurus, Pelagosaurus, Teleosaurus, Teleidosaurus, 

 Metriorliynchus, (GoniojoJtolis?, Pholidosaurus ?). 



Suborder III. Etjstjchia. 



Both the palatine and the pterygoid bones are produced into 

 osseous plates, which prolong the nasal passages backwards, and give 

 rise to secondary posterior nares, situated beneath the hinder part 

 of the skull. 



The centra of the vertebrae which succeed the atlas and axis are pro- 

 coelous, except in the two sacral vertebrae, the opposed faces of which 

 are flat, and the first caudal, the centrum of which is doubly convex. 



There is always a middle Eustachian passage enclosed between 

 the basisphenoid and basioccipital, and usually two lateral Eusta- 

 chian canals likewise enclosed by bone. 



The coracoid is elongated. 



The ala of the ilium is so low in front as to be almost obsolete ; 

 and there is a mere rudiment of an antero-dorsal process. The 

 acetabular margin is deeply notched. 



The ischium is elongated dorso-ventrally, and short antero -poste- 

 riorly. Its acetabular margin presents a deep excavation, in front 

 of which is a strong process for articulation with the pubis. There 

 are two elongated and constricted proximal carpal bones, and five 

 digits in the manus. In the pes the calcaneum has a strong back- 

 ward process, and the fifth digit is rudimentary. 



There are always more than two longitudinal series of carinated 

 dorsal scutes ; and when ventral thoraco-abdominal armour exists, it 

 contains more than eight longitudinal series of scutes. 



The ventral scutes are made up of two ossifications united 

 suturallyf. 



It is obvious, from the mere statement of the characters of these 

 three suborders, that the group which I have termed MesosucJiia is 

 intermediate between the other two. It is further plain that the 



* See d' Alton and Burmeister, ' Der f ossile Gavial von Boll,' p. 57, and 

 Taf. vii. 



t See my papers " On the Dermal Armour of Crocodilus Hasting sics," 

 Quart. Journ. Geol. Soc. 1859 ; " On the dermal Armour of Jacare and Caiman, 

 with notes on the specific and generic characters of recent Crocodilia," Proc. 

 Linn. Soc. 1859; and "Etude zoologique sur les Crocodiliens Fossiles Ter- 

 tiaires," by Dr. Leon Vaillant (Annales des Sciences Greologiques, 1872). 



