trenton limestone. 85 



Genus SC YP H OC RINUS. 



[ Greek, fl'xu9os, a little cup, and xpivo?, a lily.] 



Character. Pelvis composed of five pentagonal plates ; costal plates five, four of them 

 heptagonal, and one irregular and octagonal ; a second row of costal plates, or perhaps 

 more properly a double row of scapular plates, which are similar, uniform and quadrangular, 

 except over the irregular costal plate ; scapulae supporting a cuneiform arm-joint, inter- 

 scapular and interbrachial plates. 



It appears necessary to designate this crinoidean by a new term, since those with which 

 I am acquainted differ from it in some essential points. Disregarding any thing more than 

 general analogy and habit, we should readily refer this species to Cyathocrinus ; but 

 taking into account the details of structure, we are compelled to remove it from that genus. 



It may be found that the general characters here given can be extended so as to include 

 several others which do not fall under any constituted genus. 



125. 1. SCYPHOCRINUS HETEROCOSTALIS (n. 5p.). 



Pl. XXVIII. Figs 3 a, b, c, d, e,f. 



Body cupshaped, expanding above with five double arms ; pelvis saucer-shaped, com- 

 posed of five pentagonal plates, which are closely adhering among themselves, and to the 

 last joint of the column ; costal plates somewhat heptagonal, one of them somewhat ir- 

 regularly eight-sided ; scapulars and second scapulars subquadrangular, supporting above 

 a cuneiform arm-joint, which again sustains upon its oblique upper edges two ranges of 

 plates, which, continued, form the fingers ; interscapular plate sub-cuneiform below and 

 quadrangular above, with oblique sides which support two interbrachial plates, against 

 which the edges of the cuneiform arm-joint rest. 



The structure is fully explained by the figure 1 b, where the dotted lines connect the 

 sides of the plates as they are arranged in the fossil. 



The column is round, moderately large, and composed of joints which alternate in this 

 manner : the last joint, adhering to the pelvis, is a thin plate with crcnulated edges, which 

 is succeeded by a thicker joint with a rounded smooth edge ; again a thin one with a 

 crenuiated or fimbriated edge, and so on alternately. The entire surface of the fossil is 

 rugose or sculptured in lines and points, the edges of the plates joining by slight sutures. 



No perfect specimens have been seen, and we are ignorant of the entire length of the 

 fingers and tentacula, which were probably as long as in the last species. 



Fig. 3 a. A specimen (natural size), with the fingers and column broken off; the form otherwise well 



preserved. 

 Fig. 3 b. The structure and arrangement of the plates, the letters indicating the parts as explained in 



the previous figures. The plates are slightly enlarged beyond their natural size. 



Hf 



