Cope.] J J® [Nov. 2, 1877. 



with ridges at right angles to the sutures, which are not short. The mid- 

 dle parts of the costal bones are marked by short interrupted or inoscula- 

 ting vermicular ridges closely placed. On the middle portions of the sternal 

 bones the ridges are in places more broken, forming tubercles. 



The surface of the bridge is angularly oblique to that of the plastron. The 

 buttresses are not produced inwards. The free marginal bones are rather 

 thin, and are not recurved. 



Measurements. M. 



Length of a costal bone 110 



Width of the same. 032 



Thickness " 005 



Length of hyposternal bone 066 - 



Width of the same at inguinal notch 048 



Thickness of the same in front 007 



Found by Superintendent Lucas with the foregoing species. 



Clepsydrops limbattjs sp. nov. 



The discovery of a species of the genus Clepsydrops in Texas, in a forma- 

 tion hitherto regarded as Triassic, adds weight to the view above expressed, 

 that the Clepsydrops shales of Illinois belong either to the Triassic or Per - 

 mian formations. As typical of the new species I select a vertebra, which 

 may be exactly compared with corresponding one of 0. collettii. The 

 centrum is about as wide as long, and its sides are very concave, much 

 more so than in C. collettii, and the rim like borders of the articular ex- 

 tremities are connected by a straight compressed hypopophysial keel. The 

 sides of the foramen chordae dorsalis are convex in the longitudinal sec- 

 tion, thus contracting the opening, as compared with the very wide flare of 

 the border of one of the extremities of the centrum. This flare receives 

 the wide recurved border of the opposite extremity of the adjoining cen- 

 trum, forming a kind of ball and socket articulation. This reflected sur- 

 face forms a ridge with the funnel of the foramen at this extremity of the 

 vertebra. The concave extremity is produced downwards, so that the for- 

 amen is considerably above the middle point. The di apophysis and para- 

 pophysis are not distinct nor elongate, but are represented by a projecting 

 scar on the superior part of the centrum, which is directed downwards and 

 forwards towards the rim of the articular face. 



Besides the great contraction of the centrum, its relatively shorter form 

 distinguishes it from that of C. collettii. It is also much larger than that 

 species and the C. pedunculatus, being the largest of the genus. 



Measurements. M. 

 Length of centrum 031 



( vertical 039 



Diameter of centrum -j transverse 033 



Width of neural canal 006 



Discovered by Jacob Boll. 



Printed November 21st, 1877. 



