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) tmbricartus 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. tmbricarius 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: ‘‘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. 
vartolosus 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. wmbricarius 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. 
*I bid. 
+Geol. Surv. Canada. Vol. III, part p. 40. 
