REPORT ON THE CRINOIDEA. 329 
four, but occasionally 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 syzygial 
joints. Secondary arms (rare) of two palmar joints united by syzygy. Arms 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 
jomts. 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 arm-groove. 
The covering plates of the pinnule-ambulacra rest upon a denticulated band of limestone 
which is not fully differentiated 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, off Montserrat ; 120 fathoms. 
No. 209, off Martinique; 189 fathoms; hard bottom; bottom temperature, 493° F. 
No. 291, off Barbados ; 200 fathoms; flat calcareous stones; bottom temperature, 493° F. 
No. 295, off Barbados; 180 fathoms; hard bottom ; bottom temperature, 502° F. 
Remarks.—This interesting species, like Pentacrinus asterius, 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. Ihave only been able to examine a mutilated specimen from Montserrat, 
and three nearly perfect ones from Barbados. 
The slender cirri and their elose approximation on the stem give this type a 
more elegant appearance than Pentacrinus decorus, which is its nearest ally, these two 
being the only species with more than ten arms which have a bifascial articulation 
between the radials. The third species with this character (Pentacrinus naresianus) 
is only ten-armed ; but it has a singular resemblance to Pentacrinus blakei in the form 
of the syzygies on thearms. The stem of Pentacrinus blakei is at once distinguished from 
that of Pentacrinus decorus by the shortness of the internodes and the absence of any 
enlargement at the nodes (Pl. XXXI. fig. 3). The cirrus-sockets, too, are generally pro- 
longed downwards to a less extent than they are in Pentacrinus decorus (Pl. XXXVI); 
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 
Pentacrinus decorus. There is, however, remarkably little variation in the length of the 
(ZOOL. CHALL. EXP,—PART XXx1I.—1884.) Ti 42 
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