188 



PALiEONTOLOGY OF NEW-YOEK. 



Genus TH Y S A N C RI NU S (nov. ^cn.). 



[ Gr. Axjdmoi, fimhria, and xpivov, lilium ; from the fimbriated arms or fingers of the species included 



under this genus.] 

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

 gonal J scapular plates alternating witla the costal plates, bearing a second scapular plate, 

 and an arm-joint on which 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 the upper part. Or, the arm joint suc- 

 ceeded by a hand of one or more joints in direct succession, succeeded by 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 

 species, 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 the same plate. The fragments of arms of other 

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

 containing several species. 



582. 1. THYSANOCRINUS LILIIFORMJS (n. 5^.). 



Pl. XLII. Fig. 1 a -f. 



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

 interrupted or crenulated, sharp, elevated sti'ioe ; pelvic plates small ; 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 this species is quite peculiar and distinctive : on the plates 



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



nearly vertical striae ; and on the plates of the fingers the stride 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 



tlie 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 shown, they appear to be composed 



of a single series of plates only, since the line of joining of the two rows of the plates 



on the back is so nearly vertical. 



