PLEUROSTERNID.*. 47 



Glyptops plicatulus (Cope). 

 Plates 5, 6; text-figs. 17-17. 



Compsemys plicatulus, COPE, Proc. Amer. Philos. Soc., XVH, 1877, p. 196. BAUR, Amer. Naturalist, 

 xxiv, 1890, p. 534; Proc. Acad. Nat. Sci. Phila. 1891, p. 411; Anat. Anzeiger, xn, 1896, p. 565. 

 HAY, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 437. 



Glyptops ornatus, MARSH, Amer. Jour. Sci. (3), XL, 1890, p. 177, pi. vii, figs. I, 2; Monogr. U. S. 

 Geol. Surv., xxvn, 1897, p. 507, figs. 63, 64. 



The present species is one of the two oldest known from North America, corning as it does 

 from the uppermost Jurassic. The other species which comes from the same deposits is 

 Probaena sculpta, but it is represented by only an imperfect shell; whereas Glyptops plicatulus 

 is represented by nearly all portions of the skeleton. 



The species had for its type various fragments that had been collected for Professor Cope 

 by Mr. O. W. Lucas, at Canyon City, Colorado, from freshwater deposits that were called by 

 Professor Marsh the Atlantosaurus beds, by Scott and Knight the Como beds, and by Whitman 

 Cross the Morrison beds. Cope's type is No. 6099 of the American Museum of Natural 

 History. The principal parts present are one complete costal, apparently the third of the left 

 side (plate 5, fig. i), the proximal end of what is regarded as the fifth of the right side, the right 

 axillary region, most of the left hypoplastron, and a part of the contiguous left xiphiplastron. 

 The supposed third costal is shorter than the corresponding one of the American Museum 

 specimen, No. 336, a slightly smaller individual, as shown by the hypoplastra. It might be 

 regarded as the fifth were it not that the distal end is crost by the costo-marginal sulcus. The 

 vertebral scutes are narrower than those of No. 336. Also the bases of the rib-heads are 

 slenderer. The hypoplastral is somewhat longer and at the same time slightly narrower than 

 that of No. 336. There is a possibility that we have here two species. The sculpture appears 

 to be identical in the two specimens. Baur appears to have examined the type bones and he 

 identified them as being the same as Marsh's Glyptops ornatus. 



Professor Marsh's types of his Glyptops ornatus were obtained at Como, Wyoming, from 

 deposits regarded as of the same age as those of Canyon City. The remains consisted of a 

 skull nearly complete, portions of two other skulls, and portions of the shells of two or three 

 other individuals. These were briefly described and figured by Marsh, as cited above. The 

 figure of the skull particularly is very poor. This skull had been crusht laterally and hence 

 the figure shows it as narrower than it was in life. A side view of the same skull, prepared for 

 the U. S. Geological Survey, by F. Berger, is here presented (plate 5, fig. 2). In 1891 Dr. 

 Baur, as cited, publisht a more extended description of Marsh's specimens and criticized some 

 of Marsh's statements. The writer has examined the skull figured by Marsh. The occipital 

 condyle is broken away. The length from the condyle to the tip of the snout was close to 

 62 mm. The temporal region was originally rooft over to a perpendicular plane passing 

 through the articulations of the quadrate for the lower jaw. The extent of this roof from the 

 orbits was 38 mm. The median suture may be traced from the tip of the snout to near the rear 

 of the skull. Most of the other sutures are invisible. The supraoccipital spine appears to have 

 been destroyed. The orbit is circular, with a diameter of 12 mm. The nasals are distinctly 

 separated from the prefrontals and have a length of 4 mm. The premaxillae are small and 

 distinct from each other and from the maxillae. What bone forms the septum between the orbit 

 and the nasal cavity can not be determined. The maxilla has a thin cutting-edge and a narrow 

 triturating surface. This bone extends far behind the orbit and has a length of 33 mm. From 

 its hinder end the suture between it and the jugal may be traced upward and forward to the 

 border of the orbit. 



On the lower side of the skull is seen the anterior end of the vomer; the remainder is 

 broken away. The choanae were placed far forward. The palatines ran forward nearly to a 

 line joining the fronts of the orbits. The pterygoids are interposed between the quadrates 

 and the basioccipital. Where narrowest the pterygoid portion of the palate is II mm. wide. 

 The articulation of the quadrate for the lower jaw is concave in all directions, most so from 

 side to side. 



In the American Museum of Natural History there is a specimen of this species that was 

 collected at Bone Cabin quarry, Wyoming, about 10 miles from Como, the locality of Marsh's 



