Feb,, 1906. Carapace and Plastron of Basilemys Sinuosus. 255 



the inguinal shield which overlies the posterior or inguinal 

 buttress. 



The sculpturing of the shell in "members of this genus has been 

 variously described. In his original description* of the type species 

 B. variolosus Cope described the dermal markings as follows: "The 

 sculpture consists of round fossae, which are deeply impressed, and 

 are arranged quincuncially, so that their borders never form straight 

 lines. The latter are also more or less angulate on the edges, so that 

 the surface has a more than usually rugose character." Of the species 

 B. (Compsemys) imbricarius he writes as follows:* "The character 

 of this sculpture distinguishes the species and, in the present instance, 

 in a special manner. It consists in the C. imbricarius of excavations 

 bounded on the sides by a short ridge each, which alternate with each 

 other. Thus each bounding ridge terminates abruptly at the fundus 

 of one of the fossae, while the other end of the fossa rises and con- 

 tracts to another ridge." In the more complete specimen described 

 by Lambe as belonging to Adocus variolosus the markings are de- 

 scribed as follows :f "The sculpture consists, when most rugose, 

 of well-excavated pits of rounded hexagonal outline arranged quin- 

 cuncially; the dividing ridges are angular and narrower than the pits 

 are wide, their angularity and height being more pronounced at the 

 junction of every three pits with each other." 



It will be noted that the quotations from Cope's description of 

 B. imbricarius and Lambe's characterization of the sculpture in B. 

 variolosus describe very similar markings. Moreover, the various 

 types of markings indicated by these three descriptions are all to be 

 found in various parts of the specimen under consideration. In 

 fact, the sculpture in various regions of carapace and plastron varies 

 so widely that no area could be taken as typical with the assurance 

 that fragments from other parts of the shell could be recognized from it. 



The pittings are most conspicuous and most regular on the plas- 

 tron and about the margin of the carapace. In the vertebral region 

 they are least conspicuous and without any regular arrangement. 

 On the superior surface of the gular process and the anterior half of 

 the femoral shields there is to be found the type of sculpture described 

 in B. imbricarius in which a sharp ridge terminates abruptly at the 

 fundus of the succeeding pit. It is noticeable, however, that in those 

 portions of the femoral shields which overlie the xiphiplastra the 

 arrangement suddenly changes to a series of irregular diagonal rows. 



•Ibid. 



tGeol. Surv. Canada. Vol. Ill, part p. 40. 



