1G2 Dr. G. J. II hide on a 



definition. But undoubted examples of Hexacrinus inter- 

 scapulars, in better preservation than the Devonshire speci- 

 mens, have been figured by L. Schultze * from the Devonian 

 of the Eifel ; and though the arms are wanting in these, yet 

 they distinctly show (judging from the figures) four so-called 

 radials above the first radial, thus markedly differing not 

 only from Hystricrinus, but from nearly all the other species 

 which by Schultze and Wachsmuth and Springer are included 

 in Hexacrinus. 



The genus Hystricrinus differs from Hexacrinus, as exem- 

 plified by the typical species, in possessing only three radials 

 and in having a greater number of inter brachial plates both 

 in the anal and other interradial areas ; but more particularly 

 in the striking feature of the articulating spines and the stem 

 with its whorls of cirri. But whilst by some authorities the 

 differences in the somewhat inconstant characters of the 

 number of the radials and the interbrachial plates would not 

 be deemed sufficient to constitute a generic distinction, the 

 presence of the articulating spines, which have hitherto not 

 been discovered in any other genus of crinoids, either fossil f 

 or recent, and which constitute another link of relationship 

 between the Crinoidea and Echinoidea, might be regarded as 

 indicating a greater than generic difference, and, provisionally 

 at least, this genus may rank as the type of the family of the 

 Hy s trier inidae. 



I now pass on to describe in detail the specific characters 

 of //. Carpenteri. 



Hystricrinus Carpenteri, n. sp. 



Body cup-shaped, widest at the summit of the first radials, 

 then slightly contracting by the curving inwards of the inter- 

 brachial plates. The vault is flat or slightly convex. The 



* Denksckr. k. k. Akad. d. Wiss. Wien, Bd. xxvi. 18G7, Taf. viii. fig. 5. 



f It is a noteworthy circumstance that the aberrant Blastoid, Astro- 

 crinites Benniei, R. Etheridge, .Tun., described and figured in the Quart. 

 Journ. Geol. Soc. vol. xxxii. 1876, p. 103, pis. xiii., xiv., appears to have 

 possessed articulated spines. A small spine was discovered by Mr. Ethe- 

 rid^e adhering to one of the specimens, though not in position on the 

 tubercle ; and in a subsequent paper on this form Messrs. R. Etheridge, 

 Jun., and P. II. Carpenter record the fact that some at least of the pecu- 

 liarly ornamented tubercles, which thickly cover the surface of this 

 species, were perforated at their summits, which renders it highly probable 

 that they supported movable spines (Ann. & Mag. Nat. Hist. April 1883, 

 p. 236). 



Dr. Hambach, of St. Louis, also states that he possesses a specimen of 

 Pentremites grnnulatus, Romer, on which the coarse granules show very 

 distinct sockets for the articulation of spines (Trans. Acad. Sci. St. Louis, 

 vol. vi. no. 3, 1884, p. 543). 



