1858.] ; . HUXLEY — stagonolepis. 445 



with the characters of the exoskeleton in the CrocodiHaii Reptiles 

 can hardly fail to have his attention arrested by the remarkably 

 similar features of the scutes of Stagonolepis ; and close investiga- 

 tion shows that there is not a single peculiarity of the latter which 

 may not at once be paralleled by those of Crocodilian scutes. To 

 begin with the sculpture or ornamentation, — the outer surface of 

 the scutes exhibits distinct rounded pits, so disposed as to appear to 

 radiate more or less distinctly from a common centre, not only in the 

 modern Crocodiles, but in the Eocene Crocodilus Hastingsice and in 

 the Mesozoic Teleosauria. Wherever these scutes possess a median 

 ridge, the centre of radiation of the pits is somewhere on that ridge, 

 and the highest part of the ridge is devoid of sculpture. Next, in 

 respect of their form — the variously- shaped scutes of Stagonolepis 

 become readily intelligible when those of the existing and extinct 

 Crocodilia are understood. To this end, however, I must here in- 

 terpolate a brief disquisition upon the characters of the dermal 

 armour in the Crocodilia in general, — a subject upon which I have 

 not found it very easy to gain definite information. 



Dermal Scutes of Recent Crocodilia. — So far as my present infor- 

 mation goes, there are two modes of arrangement of the dermal 

 armour among the Crocodilia — the one characteristic of the recent 

 Crocodiles, the other known to exist in the Amphicoelian genera. 

 In the recent Crocodilia there are numerous longitudinal series of 

 dermal plates upon the dorsal region of the body. The large and 

 regular scutes are divisible into three distinct sets : nuchal, cervical, 

 and dorso-caudal. The scutes do not always overlap, and in the 

 dorsal region there may be as many as ten regular and large scutes 

 in a transverse row. Along the margins of the shield formed by the 

 regular scutes small and irregular ones are scattered. 



The ventral armour varies greatly, no osseous plates at all being- 

 developed in this region in some recent Crocodilia, while in others 

 I find the ventral shield to be very largely developed. 



In the Amphicoelian Crocodilia"^, at any rate in the Teleosauria, 

 the disposition of the dermal armour, as vrill be shown below, is very 

 different. The most numerous scutes are on the ventral surface of 

 the thorax and abdomen, where they form six longitudinal, and as 

 many as twenty transverse rows. In the dorsal region, on the 

 other hand, no distinct nuchal and cervical scutes have as yet been 

 discovered ; and in the dorso-caudal regions, the scutes, which are 

 occasionally very large, and are usually broad in proportion to their 

 length, never form more than two longitudinal rows,_ the scutes of 

 each row being suturaUy united in the middle line, and free at their 

 outer edges. There is no evidence of the existence of any scattered 



*■ The scutes of the specimen of G-oniopholis crassidens in the British Museum 

 exhibit a narrow smooth articular facet along that edge which is produced into 

 the peg ; but I am not aware that there is any evidence to show whether these 

 scutes were dorsal or ventral, or in what manner they were arranged. Their 

 sculpture consists of distinct pits ; but the peripheral pits are not particularly 

 elongated, and hence there is. no marked appearance of a radial arrangement. 



