1878.] " 5z3< [Cope. 



former at an angle. The inferior face is convex transversely, and slightly 

 concave antero-posteriorly. The tubercular rib facets are oval, and are 

 narrowed downwards and forwards. The side of the neurapophysis de- 

 scribes a curve which rises a little to the superior part of the extremity of 

 the diapophysis. The zygapophysial surfaces are as wide as long, and a 

 little oblique. The neural spine is not very elevated, and is very robust ; 

 its section is a longitudinal oval. Its summit is truncated and thickened 

 laterally. 



Measurements. M. 



„. „. rtransverse 035 



Diameter of mtercentrum < . .„_ 



I antero-postenor 023 



Expanse of diapophyses 073 



Length of tubercular surface of do 022 



Elevation of neural arch .071 



" " spine 040 



Antero-posterior diameter of summit of do 044 



Pisces. 

 Ctenodus periprion. Sp. nov. 

 This large species is indicated by a fine palatal tooth of the left side. Its 

 outline approaches that of a right-angled triangle, but the hypothenuse is 

 deeply incised by the interradial notches. The plate is rather thin, and 

 is moderately concave on the inferior face. The ridges number seven, all 

 of which are directed outwards and forwards. They are separated by 

 strong grooves, and have a perfectly smooth and uniform crest, and be- 

 come more elevated at the distal extremities. The latter are steeply de- 

 curved and serrate, both faces being invested with a polished enamel-like 

 layer. This substance is only visible in an edge view, and covers one-half 

 the depth of the margin, being excavated by the extremities of the radia- 

 ting grooves. The superior face is flat. 



The absence of serration from the radiating ridges of this species is a 

 striking feature, allying it to the genus Ptyonodus,* where the teeth are 

 wanting. 



Measurements. M. 



Length of dental plate 037 



Width " " 018 



Thickness at inner border 005 



" " external border of penultimate crest 007 



From the same locality as the species above described. 



Ctenodus porrectus. Sp. nov. 

 Two teeth of the left palate indicate this species. The tooth is char- 

 acterized by the small number of its crests (six), of which only one, 

 the very small first, is directed backwards, and the last four are di- 

 rected forwards. The crests are separated by deep grooves, which ter- 

 minate in deep emarginations. The anterior crest is produced much 

 beyond the extremity of the penultimate, and the latter as much be- 



* Proceed. Amer. Philos. Soc, 1877, p. 192. 



