70 



72 [March, 



shell much broader. From Aocyloccras? aproximans, Con. (Proceedings of the 

 Phila. Acad. p. 266,) it differs in having broadly rounded, instead of acute costae-. 

 Locality and jwxilion. Mouth Cheyenne river. No. 4. of series. 



notices of remains of extinct Reptiles and Fishes, discovered by Dr. F. V. Ilaydcn in the 

 Bad Lands of the Judith River, Nebraska Territory. 



By Joseph Leidy, M. D. 



1. Pal.bosciscus costatus, Leidy. 



The genus and species ai-e fouuded on a single specimen of a toolh of a lacer- 

 tian, discovered by Dr. Ilayden. 



The crown of the tooth is palmate, with eight radiating costfe terminating at 

 the margin in more or less developed points. The fang is flattened cylindrical, 

 and is hollow ; and it expands into a ridge surrounding the base of the crown. 

 Breadth of the crown 4 lines, length 2i lines ; width of the fang 2 lines, thick- 

 ness 1 line. Whole length of the specimen 4 lines. 



2. Trachodox mirabilis, Leidy. 



The genus and species are founded upon specimens of teeth, generally very 

 much worn and in a fragmentary condition, of a herbivorous lacertian reptile 

 allied to the lyi/anodon, discovered by Dr. Hay den. 



One of the specimens of teeth is an unworn crown, about 14 lines long and 5 

 lines in diameter at its thickest part. It has the form of a slightly bent hexahe- 

 dral column, bevelled off convexly from the summit of the tooth internally to 

 the base externally. The outer surface is smooth, and has a prominent median 

 ridge and prominent subacute lateral borders. The inner surface of the tooth, 

 presenting the five smaller sides of the column, is quite roughened with irregu- 

 lar granulations. Tlie base of the tooth is hollow, and its walls at the broken 

 border of the specimen are IJ lines thick. 



Li another and much worn specimen of a tooth, which had apparently been 

 shed, and is now 4^ lines long ; the triturating surface is slightly concave and 

 pentahedral, with concave sideS, and is 4 lines in diameter. The two portions 

 of the outer surface incline much more from the median ridge than in the pre- 

 ceding specimen ; and the base of the tooth is hollowed, apparently from the 

 pressure of a successor. 



3. Troodon pormosds, Leidy. 



The genus and species are founded on a single specimen of a tooth of a lacer- 

 tian, discovered by Dr. Hayden. 



The specimen consists of a compressed, curved, conical crown with tren- 

 chant edges. The outer side is more convex than the inner, which is worn 

 off towards the apex from friction of the opposing tooth. The trenchant edges 

 are coarsely denticulated ; the denticulations themselves being compressed 

 conical, witli trenchant edges, and are bent in such a manner that their apices 

 are directed towards the summit of the crown. The base of the tooth is hollow, 

 and is 2 lines wide and 1 J lines transversely ; and the length of the specimen is 

 3 lines. 



4. Deinodo.v horkidus, Lcid}'. 



This genus and species are founded on a number of specimens, consisting of 

 fragments of teeth of a saurian reptile, discovered by Dr. Hayden. 



Nine of the specimens referred to consist of crowns of teeth or of their sum- 

 mits, which resemble those of Mcgalosaurus, being compressed conical and 

 curved, and having trenchant, dentatcd borders. They are generally thicker 

 in relation to their breadth than in Megalosaunis, which might only be a specific 

 distinction, were it not that there are several other teeth in the same collection 

 apparently of the same animal, but quite peculiar in form. 



One of the specimens is a curved conical crown", nearly circular in transverse 

 section, having a prominent dentated ridge on each side. A second specimen 

 is a crown, deuii-elliptical in transverse section, with the posterior borders den- 

 tated. A third specimen is a small fragment of a very large tooth, apparently 



