PLASTOMENID^E. 473 



Plastomenus corrugatus Cope. 

 Plate 86, fig. 5. 



Plastomenus corrugatus, COPE, Syst. Cat. Vert. Eocene New Mexico, 1875, p. 35; Append. LL of Wheeler's 

 Report to Chief of Engineers, 1875, p. 1016 (of separata, p. 96); Wheeler's Surv. W. lOOth Merid., 

 iv, pt. n, 1877, pp. 48, 50, plate xxv, figs. 20-26; Vert. Tert. Form. West, 1884, p. 123. HAY, 

 Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 452. 



Professor Cope stated in his monograph on the fossil vertebrates of New Mexico that he 

 had remains of 6 individuals which he referred provisionally to the present species. Of these 

 he figured fragments of 2. One of these two was represented by only a portion of the left 

 hypoplastron; and this was regarded as the type of the species. It is represented by his fig. 20, 

 which is here reproduced (plate 86, fig. 5). The other bones figured were portions of costals 

 except the one represented by his figure 25. The present writer is not aware where these figured 

 specimens now are. They were collected in the Wasatch beds of New Mexico. The exact 

 locality was not designated, but it was doubtless from the Gallinas River region. 



Of the type bone, the hypoplastral, Cope makes the following statements: 



This bone is ornamented with sharp, raised, narrow ridges, which are straight or vermiculate, and 

 which inosculate but little. The broken base of the bridge is particularly stout, and the thickening 

 continues within the inguinal border to the postabdominal extremity. The inguinal edge is thinner, and 

 is incurved at the postabdominal gomphosis. 



MEASUREMENTS. 



Meter. 



Thickness of the hyposternal at middle 0.007 



Thickness of hyposternal at bridge 009 



Seven ridges measure oio 



Judging from Cope's figures of the costal bones, they presented a very different style of 

 ornamentation. Here we find what Cope has called a honeycombed structure. There were 

 apparently abruptly sunken pits, about 5 in a line 10 mm. long; while the intervening ridges 

 were about as wide as the pits themselves. Professor Cope presented no measurements of these 

 bones, so that we do not know their thickness. Altho they are so different in their style of 

 ornamentation from the type plastral bone they appear to be connected with it by the bone 

 represented by Cope's fig. 25. Cope regarded this bone as a part of the left hyoplastron; but 

 a comparison of it with the plastron of Plastomenus thomasi makes it more probably the outer 

 end of the right hyoplastron. The fig'ure ought to be inverted. 



Plastomenus communis Cope. 

 Plate 86, figs. 6-8. 



Plastomenus communis, COPE, Syst. Cat. Vert. Eocene, New Mexico, 1875, p. 35' Append. LL of Wheeler's 

 Report to Chief of Engineers, 1875, p. 1016 (of separata, p. 96); Wheeler's Surv. West lOOth Merid., 

 iv, pt. n, 1877, pp. 48, 50, plate xxv, figs. 1-3, ?4; Vert. Tert. Form. West. 1884, pp. 123, 126. 

 HAY, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 452. 



That specimen which is represented by fig. I, plate xxv, of Cope's memoir publisht in the 

 fourth volume of the Wheeler Survey, must be regarded as the type of the present species. 

 This type belongs to the U. S. National Museum and bears the catalog number 1 132. It con- 

 sists of the distal ends of a number of costal plates and a portion of the left hyoplastron. These 

 were collected by Professor Cope in Wasatch beds in New Mexico, doubtless in the region 

 of the Gallinas River. 



While the known remains of this turtle indicate a distinct species and one which may be 

 recognized when other considerable parts shall have been discovered, they do not enable us 

 to obtain an accurate idea of the animal. It must have attained a considerable size, since one 

 of the costals had a width of 44 mm. It had a thick and coarsely sculptured shell (plate 86, 

 figs. 6, 7). There were no rib-ends protruding beyond the borders of the carapace. The form 

 of the fragment of the hyoplastron (plate 86, fig. 8) present indicates pretty certainly that the 

 species belongs to the genus Plastomenus. 



