TRIONYCHID^:. 533 



44 mm. and its width close to 30 mm. It was probably only a little narrower at the anterior 

 end. It articulated with only the fifth costal. Most of the sixth neural is present. It was 

 parallelogrammic,4Omm. longand 32 mm. wide. It articulated with the hinder proximal angle 

 of the fifth costal, and the greater part of the proximal end of the sixth costal. The seventh 

 neural is partly present, and was probably about 25 mm. long and 34 mm. wide. It articulated 

 with the sixth and seventh costals on each side. It is not probable that there was an eighth 

 neural. Consequently, the seventh costals joined in the midline, as did also the eighth costals. 



The portion of the plastral bone already referred to is identified as the outer end of the 

 right hypoplastron. Its catalog number is 3886. It includes the two digitations at the external 

 angle and the remainder of the bone inward somewhat beyond the narrowest part of the bridge. 

 The width, where narrowest, is 32 mm. The length of the longest digitation is 65 mm. The 

 thickness at the free border equals 12 mm.; that thru the narrowest part of the bone, 23 

 mm. The distal free border is beveled ofF. The lower surface of the bone is furnisht with a 

 sculpture consisting of coarse pits and ridges, arranged, where well preserved, in rows parallel 

 with the outer border. 



Amyda crassa appears to resemble somewhat A. uintaensis (Leidy), but it differs in various 

 ways. The latter species has its greatest breadth somewhat behind the middle of the length. 

 The nuchal bone of A. crassa is longer, from side to side, in proportion to its width. The 

 neurals of Leidy's species are narrower and with more nearly parallel sides. Moreover, there 

 were only 6 neurals, whereas, in A . crassa, there are 7- 



Two costal bones, No. 1021 of the American Museum, found in 1895, near the top of 

 division B of the Uinta beds, belong apparently to this species. They indicate a greater con- 

 vexity of the carapace than is shown by the type. 



Amyda? lima Cope. 

 Plate 98, fig. n. 



Trionyx lima, COPE, Proc. Acad. Nat. Sci. Phila. 1869, p. 12; Amer. Naturalist, in, 1869, p. 90; Trans. 

 Amer. Philos. Soc., xiv, 1869, pp. 151, 153, plate vii, fig. 14; Proc. Amer. Philos. Soc., xiv, 1875, 

 p. 363. HAY, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 454. 



The original description of this species is exceedingly brief, and was not accompanied by 

 a figure. A sufficient description and figure were, however, publisht in the same year. The 

 type and only known specimen, now in the American Museum of Natural History, is a frag- 

 ment of the distal end of one costal. It is remarkable for its heavy construction. The bone 

 was somewhat decayed and eroded; and it is not certain that we have present either of the 

 sutural borders. It is probable, however, that we have nearly the original width of the bone. 

 The present width is 47 mm. The thickness, which includes the rib, is 18 mm. Even near the 

 supposed sutural border the thickness is 14 mm. The rib probably projected somewhat, but 

 how much can not be determined. At the free border the bone is cut off at nearly right angles 

 with the upper surface. The under surface stands out somewhat farther than the upper, so 

 that there is a shallow groove occupying the free border. 



As Cope suggests, the most conspicuous character of this species is found in its sculpture. 

 This consists of rather high and narrow ridges which run across the bone, and separate grooves 

 which are somewhat wider than the ridges themselves. The summits of the ridges are uneven 

 and are sometimes cut quite to the bottom. There are remarkably few connecting ridges; 

 but occasionally a ridge is found to divide; or it may suddenly come to an end. The distance 

 across two grooves is about 7 mm. On the proximal end of the fragment the ridges are some- 

 what irregular in their course; at the distal end they are narrow and much interrupted. 



In the American Naturalist, Professor Cope remarks concerning this species: 



The Trionyx of our Miocene (T. lima Cope) was large and rough, with narrow ridges. Its remains 

 occur with dolphins and porpoises, but it may have been floated or washed from the mouth of a 

 freshwater stream into such strange company. 



There are, however, reasons for believing that some species of the Trionychidae are not 

 averse to living in salt water. 



This species was found in the Miocene marl, in Cumberland County, New Jersey. 



With so little of the skeleton of this species for examination, it is impossible to determine 

 with any degree of certainty the genus to which it belongs. 



