DERMATEMYDID^:. 23 1 



lower surface of the plastron; at the femoro-anal sulcus, only 20 mm. On the upper surface 

 of each xiphiplastron is a scar for the pubis. This scar is 55 mm. long and 30 mm. wide. 

 The inner borders of the two are 100 mm. apart. The hinder end of the lobe is truncated 

 and bent upward as the hinder extremity is approacht. 



The median portion of the plastron is very concave, a condition which appears to indicate 

 that the individual was a male. 



On some parts of the plastron the sulci bounding the epidermal scutes are very distinct; 

 in others they are obscure, but determinable. They consist of very narrow, thread-like grooves, 

 some of which pursue their course at the bottoms of broad channels, while others keep on 

 the level of the general surface. The median sulcus runs an extremely irregular course, being 

 first on one side of the midline, then on the other. The intergulars occupy the whole lower 

 surface of the lip, extending backward too mm. along the midline. The gulars meet at the 

 midline a distance of 35 mm. Their posterior borders run parallel with the anterior. 



At the midline the numerals join for a distance of only 8 mm.; but from this they expand 

 rapidly and their outer ends reach about 60 mm. behind the axillary notch. The pectoral 

 scutes are, fore and aft, extremely broad, meeting along the midline a distance of 195 mm. 

 Their outer ends are only 30 mm. wide. The abdominal scutes extend along the midline 160 

 mm., while their outer borders are 240 mm. long. The length of the femorals at the midline 

 may be taken as 90 mm.; that of the anals as the same. 



The scutes covering the bridge are separated from the plastral scutes just described by a 

 nearly straight sulcus running from the axillary to the inguinal notch. Of these scutes the 

 most anterior and the posterior alone appear to represent the inframarginal series. The 

 others are bridge marginals. Of these, one, the sixth marginal, has become greatly expanded 

 at the abdominal end; the other marginals are greatly narrowed at their lower ends. This 

 absence of a series of inframarginals is remarkable in this family. 



The sculpture of this species resembles closely that of its predecessor, B. variolosa. The 

 carapace and the plastron are both rough with sharp elevations, which are usually triangular 

 pyramids. These are mostly arranged in rows, of which three or four are spanned by a line 

 10 mm. long. 



The present species differs from B. variolosa in various points. The gulars of the Judith 

 River species are crowded far from the median line; in B. sinuosa they are in contact with 

 each other. The pectoral scutes of B. sinuosa extend backward nearer to the hyohypoplastral 

 suture than they do in B. variolosa. The hinder extremity of the plastron of B. sinuosa is trun- 

 cated, bent upward somewhat, and has its borders acute; that of B. variolosa is broadly 

 rounded, flat, and the borders are thick and obtuse. From some peripherals present, belonging 

 to the type of B. variolosa, it appears that the sculptured, horn-covered surfaces on the under 

 side of the peripherals are considerably broader than they are in B. sinuosa. On the eighth 

 peripheral this surface is 70 mm. wide; in B. sinuosa it is only 50 mm. wide. The plastron 

 of the type of B. variolosa is only about 10 mm. longer than that of B. sinuosa Riggs. 



A fragment of the epiplastral lip of what is regarded as this species was found by Mr. 

 Barnum Brown of the American Museum, on Hell Creek, Dawson County, Montana. 



Basilemys imbricaria (Cope). 

 Plate 32, figs. 5, 6, 7; teit-figs. 290, 291. 



Compsemys imbricarius, COPE, Proc. Acad. Nat. Sci. Phila. 1876, p. 257; Bull. U. S. Geol. Surv., HI, 



1877, P- 573- 

 Basilemys imbricarius, HAY, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 445. HATCHER, Bull. U. S. 



Geol. Surv. No. 257, 1905, p. 77. 

 Adocus (Basilemys) imbricarius, OsBORN, Cont. Canad. Palaeont., HI (4 to )> I 9 O2 > P- T 6- 



This species was founded by Professor Cope on very unsatisfactory materials. The type, 

 to which only three fragments (No. 6102 of the American Museum of Natural History) can be 

 referred with any certainty, was found in the Cope collection mingled with fragments of two 

 or three other species. The identified bones are here figured of the natural size (plate 32, 

 n g s - 5. 6, 7). All are probably portions of costal plates. The larger piece is traverst by a 

 narrow and sharply imprest sulcus, and appears to be the fragment mentioned by Cope as 



