74 [March, 



important peculiarities, and Tve regarded it as hAng merely a species of Pcntre- 

 miLcs (tiay.) analogous to (/'. Eta-acrinuH) Verneuili (Rcjumer.) Afterwards, 

 through the politeness of 8. A. Casseday, Esq., of Louisville, we were put in 

 possession of two individuals in a more perfect state of preservation, and these, 

 with some specimens since found by ourselves, have furnisEed the material 

 from which we are enabled to add a new and interesting genus to the farail}' 

 Blastoidea. 



Eleutherocrincs, Noi\ Gen. 



Agreeable to the plan pursued by Messrs. D'Koniiick and Le Hon, we give as 

 the formula of the genus 



Bufiul pin'ca, 3. (hie small, two irregular and very much elongated. 



Radial picccx, 1 x i>- -Four-forked, occupying nearly the whole length, one short 

 and not forked. 



Interradial pieces, 1 X 5. Small. 



Fseudoambulacral areas, 5. Four linear extending nearly the entire length of 

 the caly.K, one short, sub-triangular, situated on the summit plane. 



Column, none. 



Ovunal aj.>ertures, 8 (?) 



Generic characters. The calyx is of an elliptical form, truncated at summit and 

 sub-triangular at base. 



The base is very irregular in form, sub-triangular at its lower part, and pro- 

 longed on one of its sides to a remarkable length, It consists of three pieces, 

 one of which is small, lozenge-shaped ; the other two are precisely alike, very 

 large and prolonged nearly to the middle of the cal^x. These latter pieces are 

 joined together in the median line by a straight suture, with which their exter- 

 nal edges are sub-parallel, except the inferior fifth, which exhibits a small angu- 

 lar fold, directed obliquely forwards to articulate with the inferior edges of the 

 single basal piece. The superior edge of this fold is also emarginated to receive 

 the extremity of an elongated radial piece. 



Radial pieces. Four are non-symmetrical, occupy nearly the entire length of 

 the calyx, and are channelled almost to the base for the reception of the pseudo- 

 ambulacraj. The middle -air alternate with the single basal, the exterior ones 

 repose on the emarginated edges of the fold of the large basals. The fifth radial 

 piece scarcely exceeds one-half the length of the others, though it is much 

 wider. It rests on the upper edges of the large basals and between the superior 

 half of two of the long radials. Its upper edge reaches to the level of the sum- 

 mit plane. The surface is destitute of a pseudo-ambulacral groove. 



Interradial pieces, five, small, alternating with the radials. Three of them are 

 somewhat lozenge-shaped ; two irregular in form, articulate, with the short 

 radial piece. 



Fseudoambulacral areas, four are linear, commence at the central summit, open- 

 ing and descend nearly to the base ; the fifth is triangular and lies horizontally 

 on the summit jilane just within the edge of the short radial piece. 



Ovarial apertures. Only eight of tnese openings are visible in the specimens 

 under examination ; two are situated at the extremity of each lozenge-shaped 

 interradial, each pair being divided by a mesial se{)lum ; but at the extremity of 

 each irregular interradial there is apparently merely a simple round opening 

 without any visil)le septum. No anal opening is to be seen in our specimens. 

 Moulh nearly central. 



Column. No trace of an aperture or articular facet exists at the base to indi- 

 cate that the genus possessed a column. 



Electherochinos Cassed.\yi. Nov. sp. 

 The body of this species is of an ellipsoidal form, truncated at summit, sub- 

 triangulai below, and flattened on that portion of the circumference occupied 

 by the large basals and short radial. The surface of all the principal pieces is 

 marked with numerous delicate striaj, slightly tlexuous and running in a direc- 

 tion nearly parallel with the edges. 



