212 PALiEONTOLOGT OF NEW-YORK. 



Genus STEPH ANOCRINUS (Conbad). 



The following is Mr. Conrad's description of this genus : 



" This singular fossil may be described as having five sides, each of which is depressed and 

 " angulated, the angles profoundly carinated ; three of the sides with an oblique carina ; three 

 " longitudinal articulations only visible ; ambulacra on the upper surface, and five in number ; 

 " from the margin proceed five elevated, angular, spiniform processes ; pelvis or base trian- 

 " gular, with a cavity where the column unites with it ; canal probably pentangular, and very 

 " small." 



This description alone does not convey a very accurate idea of the structure of this very 

 remarkable crinoid, which may be characterized as follows : 



Column round, with a round canal ; base triangular, composed of three pelvic plates, suc- 

 ceeded by five costal plates, on the upper sloping edges of which rest in alternation five 

 scapular plates, which are extended above into angular spiniform processes ; the upper margins 

 of the costal plates are excavated in the middle, and on their inner margin support a small 

 semicircular plate ; each of these little plates supports two narrow elongated plates or ribs, all 

 converging towards the centre, and sustaining in part the five pentagonal plates of the proboscis 

 or aperture ; these five pentagonal plates have their bases resting, in the centre, upon the inner 

 narrow side of the spiniform terminating plate of the outer series, while the sloping basal 

 margins rest upon the elongated ribs before mentioned ; on one side of the centre, and on the 

 inner face of one of the spiniform plates, is an ovarianC?) aperture, protected by five elevated 

 triangular plates. 



This structure, in all its essential particulars, exists in two very distinct species which have 

 been examined. A structure not very dissimilar exists in some of the so called Pentremites 

 from the Carboniferous limestone*. 



599. 1. STEPH ANOCRINUS ANGULATUS. 



PL. XLVIII. Fig. la-m. 

 Stephanocrinus angulatus. Conbad, Jour. Acad. Nat. Science, Vol. viii, pag. 279, pi. 15, fig. 18. 

 Column round, composed of thick equal joints which are rounded on the exterior margins, 

 articulating surfaces crenulated near the outer margin ; canal minute, round ; form of the body 

 reverse-pyramidal, spreading more or less gradually from the base upwards ; sutures between 

 the plates scarcely visible ; base triangular, depressed towards the centre, which is occupied 

 by the minute round column ; pelvic plates three, equal at the base, one of them pentagonal 

 the other t'w'o heptagonal, the vertical sides being equal, the pentagonal plate two-sided, and 

 the other two each four-sided above ; the width of the hepatagonal plates on the upper margin 



• The Genus Pentremites, in its usual signification, includes fossils of at least three distinct genera. 



