188 PALEONTOLOGY OF NEW-YORK. 



Genus TH Y S ANO C RI NU S {ncv. ge7i.). 



[Gr. hictvoi, Jimhria, aud xpivov, I ilium ; from (ho finiliriatod arms or fingers of tho species included 



under this genus.] 



Column round ; pelvis composed of five jientagoual jdatos ; costal plates five, hexa- 

 gonal ; scapular plates alternating with the costal plates, bearing a second scapular plate, 

 and an arm-joint on whicli the subdivisions of the arms take place ; a single interscapu- 

 lar and two second interscapulars; arm divisions composed of a single series of plates in 

 the lower part, and a double alternating series in tlie upper part. Or, the arm-joint suc- 

 ceeded by a hand of one or more joints in direct succession, succeeded l^y fingers com- 

 posed of a double alternating series of joints. 



The essential characters here presented, it is believed, will be found in a number of 

 si^ecies, all having the arms composed, particularly in the upper portions, of a double 

 series of joints with jointed tentacula. The interscapular plates will probably not be 

 found constant in all species, but they are clearly present as described in the specimen 

 fig. 1 a, pi. 42, and also in fig. 4 6 of tlie same plate. The fragments of arms of other 

 species with tentacula having similar characters, show the groui> to be a natural one, and 

 containing several species. 



582. 1. THYSANOCRINUS LILIIFORMJS («. .v;).). 



Pl. XLII. Fig. la-/. 



Body cup-form, subangular ; surface of plates ornamented by vertical or radiating, 

 interrupted or creniilatcd, sharp, elevated strice ; pelvic plates ^mall ; costals larger, and 

 succeeded by five still larger scapular plates, from which in direct series originate the 

 arms and fingers ; arm-joints succeeded by three simple hand-joints ; fingers composed 

 of a double series of joints, fimbriated ; column round, composed of alternating thicker 

 and thinner joints, which are more irregular near the base of the cup. 



The surface ornament of tliis species is quite peculiar aud disiiuctive : on the plates 

 near the base it is radiating, and sometimes granular; on the higher plates, interrupted, 

 nearly vertical stri?e ; and on the plates of the fingers the striae extend quite across the 

 plate somewhat obliquely, and are sometimes granulated. The structure and arrangement* 

 of the plates, to the commencement of the arms, are only of generic importance, though 

 the forms are slightly different from another species. The joints of the fingers are wide, 

 and the tentacula are quite distinctive when compared with others, as shown on the 

 same plate. The first joint is narrow and long, very gradually tapering; the succeeding 

 Joints are somewhat longer than the first, distinctly angular, with the angles crenulate 

 or asperate. 



Where the fingers are crushed, and one side only f^hown, they appear to be composed 

 of a single series of plates only, since the line of joining of tlie tw'o rows of the plates 

 on the back is so nearly vertical. 



