PROCEEDINGS OF GEOLOGICAL SOCIETIES. 



47 



those more characteristic parts upon which the conclusions of the author of the 

 paper, respecting the structure and affinities of Stayonolepis, are based. 



They were, — 1. Dermal scutes ; 2. Vertebrse ; 3. Ribs ; 4. Bones of the ex- 

 tremities ; 5. Bones of the pectoral arch. ; and 6. A natural cast of a mandible with 

 teeth. The dermal scutes are all characterized by an anterior smooth facet, over- 

 lapped by the preceding scute, and by the peculiar sculpture of their outer surface, 

 Avhich exhibits deep, distinct, round, or oval pits, so arranged as to appear to 

 radiate from a common centre. Of these scutes there are two kinds, the Hat and 

 angulated. By a careful comparison with the dermal armour of ancient and 

 modern crocodilian reptiles, it was shown that eveiy peculiarity of the scutes of 

 Stagonolepis could find its parallel in those of Crocodilus or Teleosaur us; the flat 

 scutes resembling the ventral armour of the latter ; the angulated scutes the 

 dorsal armour of the former genus. 



An unexpected verification of the justice of this determination was furnished by 

 a natural cast of a considerable portion of the caudal region of Stagonolepis, con- 

 sisting of no less than seven vertebrge, enclosed within the coiTesponding series of 

 dermal scutes. Of these, the dorsal set were angulated ; the ventral, flat. 



It would appear that the anterior dorsal scutes attained a very considerable 

 thickness, while the more posterior scutes Avere widest — attaining more than five 

 inches in breadth in some instances. The vertebras described were all studied 

 from natural casts, and belonged to the caudal, sacral, and anterior dorsal series. 

 These vertebrae are, in their leading features, similar to those of Teleosaurians ; 

 the obliquity of the articular faces of the centra, so characteristic of the vertebrae 

 of Stagonolepis, being, as the author of the paper pointed out, a very common 

 character of Teleosaurian, and even of modern Crocodilian, vertebrae. Of the 

 sacral vertebrae, only a natural cast of the posterior face of the second had been 

 obtained ; but it was sufficient to demonstrate the .wholly crocodilian characters of 

 this region in Stagonolepns. 



The dorsal verteljrae present a remarkable peculiarity in the strong upward, 

 outward, and backward inclination of the transverse processes, and in the size of 

 the facet for the head of the rib. The vertebrae thus acquires a Dinosaurian 

 character ; but no great weight Avas attached to this circumstance, as the amcwnit 

 of upward inclination of the transverse processes of the anterior dorsal vertebn^ 

 varies greatly in both Crocodilia and Enaliosauria. 



The ribs have well-marked and distinct capitula and tubercula ; and the scapula 

 is extremely like that of a crocodile. Tlie femur, though somcAvhat thick in pro- 

 portion to its length, and though its articular extremities present such a peculiarly 

 eroded appearance as to lead to the belief that they Avere covered Avith thick car- 

 tilaginous epiphyses, is also completely crocodilian in its clraracters. 



The natural cast of the mandible is remarkable for the great length and sub- 

 cylindrical contour of the teeth, the apices of which are slightly recurved. The 

 surface of the tooth is marked by numerous close-set longitudinal gTooA^es, which 

 all terminate at a short distance from the smooth apex, it Avould appear that the 

 teeth contained large pulp-cavities, and that each Avas set in a deep and distinct 

 alveolus. NotAvithstanding their special peculiarities, these teeth might m many 

 respects be compared Avith those of the Teleosauria. 



A metatarsal or metacarpal bone, reproduced from a natural cast, was shown to 

 be similar to that of a crocodile, l)ut so much shorter in proportion to its thickness 

 as to indicate an altogether shorter and broader foot. The cast of an ungual 

 phalanx, on the other hand, proves that Stagonolepis had long and taper claws. 



Thus far the resemblances Avith the Crocodilia are, on the whole, very close ; 

 but the characters of a coracoid obtained from Lossiemouth, separate Stagonolepns 

 fi'om all knoAvn recent and fossil Crocodilia. It is, in fact, a lacertian coracoid, 

 very similar to that of Hyheosaurus. 



In summing up the evidence thus brought forward as to the affinities of Stagono- 

 lepis, the author, after comparing it with the oldest knoAvn Reptilia, expressed his 

 opinion that the peculiar characters of this ancient reptile separate it as widely 

 from the mesozoic ReptUia hitherto discovered, as these are separated from the 

 cainozoic members of the same group, — in fact, it Avidely diverges from all knoAvn 

 recent and fossil forms, and throAvs no clear light on the age of the deposit in 

 Avhich it occurs. 



