HUDSON-RIVER GROUP. JJSl 



Gends GLYPTOCRINUS. 



[Greek, yXwrrof, sculptured, and xpivo;, a lily; in allusion to the deeply carved or sculptured plates of 



the body.] 



Character. Column round ; pelvis composed of five plates ; costals in two series, with a 

 single regular intercostal plate ; scapulars five, with two interscapular plates ; scapulars 

 supporting a pair of arm-plates, which are succeeded by the hands and fingers. 



340. 1. GLYPTOCRINUS DECADACTYLUS. 



Pl. LXXVII. Figs. I a -/; and Pl. LXXVIII. Figs. 1 a - «. 



Body cupshaped, with ten arms, which support twenty tentaculated fingers ; plates all 

 marked by strong elevated radiating ridges ; pelvic plates five, pentagonal, supporting upon 

 their upper oblique edges five heptagonal costal plates, which are succeeded by five 

 hexagonal second costals in a direct line ; scapular plates heptagonal, resting directly upon 

 the straight upper side of the second costals, and supporting on their two upper oblique 

 edges two hexagonal arm-joints, which in turn support a second arm-joint, and this one two 

 hexagonal hand-joints, the latter sustaining the fingers ; fingers composed of a column 

 of fimbriated joints, which are quadrangular below and cuneiform above ; column round 

 or obtusely pentagonal, varying in its character at different distances from the body. 



In addition to the regular series of plates supporting the arms and fingers, there are 

 numerous intermediate ones, of which a hexagonal intercostal plate, a first pair of hexa- 

 gonal interscapular plates, and a second pair of heptagonal interscapular plates, the latter 

 truncated above, are always regular and uniform. Between these last interscapular plates, 

 there is usually an irregular interscapular joint, and several pectoral plates. The number 

 and arrangement of the latter does not appear to be always uniform ; but I have not been 

 able to find specimens where every part could be satisfactorily examined. Between each 

 pair of arms there are three or more plates, and between each pair of fingers one or more 

 plates at tiie base. The capital plates, and their arrangement, are shown in the enlarged 

 figure of the crown, fig. 1 d, pi. 77. The mouth is depressed and obscure. 



The body of this species is readily recognized by the strong radiating ridges which mark 

 the surface of all the plates below the tentaculated fingers. The surface is also marked by 

 five more prominent ridges, which, proceeding from the first costal plates, bifurcate on 

 the scapular plate, the divisions extending to the base of each pair of fingers. In these 

 characters of the surface, and in "its general structure, it resembles some species of the 

 Genus Actinocrinus, from which it differs in having five instead of three pelvic plates.* 



* The first notice of this fossil was given by Mr. J. G. AirrHomr of Cincinnati, in Siu.iman's American Journal 

 tif Science, 1838, Vol. xxxv, p. 405. Mr. A. gives a very good figpre of this beautiful species, but proposes no namej 



[ PALiBONTOLOGY.] 36 



