CONTRIBUTIONS TO PALEONTOLOGY. 339 



Now the specimen of this species which I have examined, and which 

 I suppose to be the one figured upon Plate x, figures 3 a, 3 5, has the ambu- 

 lacral plates alternating ; and however these minute structures may 

 present themselves to our eye, I believe that we have in no Echinoderm 

 two adjacent series of plates which are precisely opposite one another. 



In the specimen of T. cylindricus examined, the ambulacral plates ai'e 

 less distinctly alternate ; but the relation of the adambulacral plates and 

 the pores are the same as in the other form. Not having seen the 

 specimen showing the dorsal view, figure 4a of Plate x, I can only 

 remark that the structure of the rays is very similar to that of Peotaster. 

 If the appearance of a disc be fallacious, then we have in T^eniaster a 

 structure in all respects similar to that of Peotaster, wanting the disc. 

 If the structure of Peotastee, as represented by Mr. Saltee be the true 

 one, then the New York species must be referred to another genus. Not- 

 withstanding the difference shown between the figures of Prof Foebes 

 and Mr. Saltee, and between these and the illustrations here given, I 

 am still inclined to believe that our species is congeneric with the original 

 of Prof Foebes' type of that genus. 



GENUS LEPIDECHINUS, Hall. 



Lepidbohinus, Hall. Descript. New Species of Crinoidea; Preliminary Notice, p. 18. 1861. 



This genus was described as " Subspheroidal, the form and arrange- 

 ment of the ambulacral and interambulacral series as in Palechinus, with 

 the plates of the interambulacral series imbricating from the dorsal side, 

 and the lower edges of each range overlapping those below ; while the 

 plates of the ambulacral areas are imbricating in the opposite direction, 

 narrow and deeply interlocking at their joining edges, each plate pierced 

 near the opposite extremity by two pores. Surface granulose." 



This genus was separated from Palechinus on account of the imbricating 

 character of the plates, both of the ambulacral and interambulacral areas, 

 and also fromr-the more numerous ranges of plates in the interambulacral 

 areas. In its essential characters, it is much further removed from that 

 genus.* 



* Dr. B. F. Shumakd, in his Catalogue of Palaozoic Fossils, in adopting the generic name 

 Lepidbchinus, adds : " Compare Oligoporus (Meek & Worthbn)." I am at a loss to under- 

 stand any near analogy between a fossil having the " ambulacral areas about half as wide as the 

 interambulacral spaces," and the "ambulacral pores in four ranges with some irregular inter- 

 calated smaller pieces between," and one having the pores in pairs, two to each piece, and arranged 

 in four double rows, two on each side of the mesial ridge or convexity of each ambulacrum. 



