REPORT ON THE CRINOIDEA. 329 



four, but oceasioually three or five to each ray. Primary arms of one to four distichal 

 joints, of which the first two are united by a ligamentous articulation. The second one 

 bears a pinnule, and the next may be either a simple axillary or consist of two syzj^gial 

 joints. Secondary arms (rare) of two palmar joints united by syzygy. Anns of about 

 ninety slightly overlapping joints, nearly oblong at first, but afterwards becoming more 

 unequal sided. The first free brachial bears a pinnule, and the second is usually a 

 syzygial joint, while other syzygies occur on the arms at intervals of two to twenty 

 joints. The proximal face of the epizygal forms a sharp angle which projects backwards 

 into the retreating distal face of the hypozygal. 



The lowest brachial pinnules consist of seventeen or eighteen joints, the first six of 

 which are rather broad, and the later ones more slender. Farther out on the arm this 

 inequality gradually disappears, all the joints but the first two being moderately long and 

 narrow. The disk, so far as visible, is covered with small, closely set plates which extend 

 on to the arms, covering the muscular bundles at the sides of the narrow aiTu-groove. 

 The covering plates of the pinnule-ambulacra rest upon a denticulated band of limestone 

 which is not fully difi'erentiated into side plates. 



Colour in spirit, yellowish-white. 



Localities. — All in the Caribbean Sea. From the dredgings of the U.S. Coast 

 Survey steamer " Blake." Cruise of 1878-79. No. 157, ofi" Montserrat ; 120 fathoms. 

 No. 209, ofi" Martinique; 189 fathoms; hard bottom; bottom temperature, 49|° F. 

 No. 291, ofi" Barbados ; 200 fathoms ; flat calcareous stones; bottom temperature, 49|° F. 

 No. 295, off Barbados ; 180 fathoms ; hard bottom ; bottom temperature, 50|° F. 



Remarhs. — This interesting species, like Pentacrinus asterms, appears to be some- 

 what rare, having only been dredged four times by the " Blake"; and it has never, so far 

 as I know, been obtained by Mr. Damon's agents, as the other three West Indian .species 

 have been. I have only been able to examine a mutilated specimen from Montserrat, 

 and three nearly perfect ones from Barbados. 



The slender cirri and theii- close approximation on the stem give this type a 

 more elegant appearance than Pentacrinus decorzis, which is its nearest ally, these two 

 being the only species with more th-an ten arms which have a bifascial articulation 

 between the radials. The third species with this character (Pentacrinus naresianns) 

 is only ten-armed ; but it has a singular resemblance to Pentacrinus hlahei in the form 

 of the syzygies on the arms. The stem of Pentacrinus hlaJcei is at once distinguished from 

 that of Pentacrinus decorus by the shortness of the internodes and the absence of any 

 enlargement at the nodes (PI. XXXI. fig. 3). The ciiTUS-sockets, too, are generally pro- 

 longed dowTiwards to a less extent than they are in Pentacrimis decorus (V\. XXXYL); 

 though Pentacrinus blakei shows a considerable amount of variability in this respect, some 

 sockets having almost no downward extensions at all, while others are more like those of 

 Pentacrimis decorus. There is, however, remarkably little variation in the length of the 



(ZOOL. CHALL. EXP. PART XXXII. 188-1.) ^' ^'-^ 



