178 DR. A. s. wooDAVARD ON EXTINCT [Mar. 5, 



show that this element overlapped the maxilla to a considerable 

 extent. Ihe maxilla itself (mx.) is relatiAely large, and best 

 preserved on the right side. It is stout and curves inwards in 

 front. It articulates not only with the pterygoid behind by the 

 intervention of the transverse bone, but also with the palatine by 

 a broad articular palatal process which extends inwards from its 

 middle. It likewise articulates directly with the prefrontal in an 

 extensive suture. It shows 14 or 15 large shallow sockets for the 

 implantation of teeth (fig. 1 b) ; and one dental crown preserved at 

 the hinder end of the left maxilla is very slender and recurved. 

 The fragmentary remains of the mandible show it to have been 

 of the usual slender ophidian type, with a very loose articulation 

 between the dentary (c?.) and articulo-aiigular region («<7.) ; and 

 the dentary exhibits a sex'ies of large shallow tooth-sockets like 

 those of the maxilla. 



Behind the skull there are remains of a long series of typical 

 ophidian vertebrae, which do not present anj^ features worthy of 

 special note. The neural arches are shown to have borne delicate 

 low spines, though nearly all of these have been broken away and 

 are only represented by their bases in the fossil (Plate XX. fig. 2, ii.). 

 The ribs (r.) are very stout. 



Erom this description it is evident that the Patagonian fossil in 

 question represents a typical member of the order Ophidia. As 

 shown, however, by the conformation of the occiput and the 

 relatively small size of the quadrate, it belongs to one of the more 

 generalized types. Its closest allies may therefore be sought 

 among the Boidae and Ilysiidse, which still constitute so large and 

 characteristic a part of the Ophidian fauna of South America. 

 The skull bears much general resemblance to that of a Boa con- 

 strictor, but is readily distinguished from the latter by its non- 

 projecting supratemporal and relatively small quadrate. It is 

 similarly distinguished from the skull of all the other Boidse \ In 

 precisely this character, on the other hand, the fossil skull agrees 

 with that of the existing Ilysiidee ; and its occipital region is 

 almost identical with that of the South American genus Ilysia ^. 

 The resemblance to the latter, indeed, is so close that, although 

 the coronoid region of the mandible is not observable in the fossil, 

 there need be little hesitation in referring the extinct type now 

 described to the family Ilysiidse, It differs from the existing 

 genera of the family in its more numerous marginal teeth and 

 relatively smaller palatine teeth ; in its elevated sagittal crest ; 

 and in the presence of well-developed neural spines on the 

 vertebrae. It also differs from the South American Ilysia, though 

 agreeing with the Javan Cylindropliis, in the possession of a small 

 postfrontal bone. It may, in fact, be regarded as a comparatively 

 gigantic forerunner of the Ilysiidae, analogous to Glyptodon 

 among the Armadillos and Pliororhachos among the Cariamas. 



1 G. A. Boulenger, Catalogue of the Snakes in the British Museum (Natural 

 History), vol. i. (1893). 



3 G, A, Boulenger, torn. cit. (1893), p. 132, fig. 8, 



