326 THE VOYAGE OF H.M.S. CHALLENGEE. 



obtained at Station 210, where four individuals of two species of Pentacriniis were 

 dredged (see \). 128) ; but, as in the case of Pcntacrinus alternicirrus, I can only infer 

 this from the fact that these two species, together with the single specimen of 

 Metacrinus murrayl, were the only ones which came into my hands without any record 

 of locality ; while there were none with the label of Station 210. 



Remarks. — Pentacriniis naresianus is remarkable as being the only recent species of 

 the genus in which there are not more than ten arms ; while the shape of the arm-joints, 

 especially the lower ones (PL XXVIII. fig. 1; PL XXIX; PL XXX. fig. 1), is also 

 more oblique than is usually the case in the Pentacrinidse, so that in both respects it 

 approaches the Comatulse. Apart from these characters and the well plated ambulacra 

 (PL XXVII. fig. 13), the arms are readily distinguished by the peculiar form of the 

 syzygial unions. AVhen seen from the dorsal side (PL XXIX. fig. 1 ; PL XXX. fig. 1), 

 the distal edge of the hypozygal appears to be very convex and to project strongly 

 forwards into the epizygal ; while in a side view (PL XXX. fig. 23) the epizygal shows 

 a sharp backward projection into the hypozygal. When the syzygial faces are exposed 

 (PL XXX. figs. 20, 21), a sharp angle appears across the middle of the proximal face of 

 the epizygal ; and the distal face of the hypozygal has a corresponding re-entering angle, 

 so that the two joints interlock very closely. Essentially the same form of syzygy 

 recurs in Pentacrimis blcd-ei of the Caribbean Sea (PL XXXII. figs. 5, 7, 12, 14) ; but 

 the other characters of this species are entirely difi"erent from those of Pentacriniis 

 naresianus, as it has twenty to thirty arms and a more slender stem with shorter 

 internodes (PL XXXI. ). 



These two species, together with Pcntacrinus decorus, are the only three recent 

 Pentacrinidge in which the two outer radials and the two first joints beyond them are 

 united by bifascial articulation. The articular faces of these joints in Pentacrirms 

 naresianus are shown in PL XXX. figs. 11, 12, 16, 17. It further resembles Pcnta- 

 crinus decorus in the pyriform downward prolongation of the cirrus-sockets over the 

 infra-nodal joints, the upper faces of which are markedly stellate in consequence 

 (PL XXX. fig. 29). The nodal joints, however, are not produced outwards at the angles 

 between the cirrus-sockets, nor do they slope outwards from their upper edge to the top 

 of the sockets ; so that the general outline of the stem is very even (PL XXVIII. fig. 2). 

 But in Pcntacrinus decorus this enlargement of the nodal joints is very perceptible in 

 mature individuals (PL XXXVI. ; PL XXXVII. figs. 1, 2), though not in the youngest 

 (PL XXXA^.). On the other hand, it appears in the youngest specimens of Pentacrinus 

 naresianus (PL XXXa. fig. 5), though disappearing some time before maturity is reached. 



Pentacriims naresianus also presents a considerable variation in the size and shape 

 of the basals, which is so very remarkable a character of Pentacrinus decorus. In aU 

 the four figures of the calyx which were drawn for Sir '\Vy\'ille Thomson (Pis. XXVIII.- 

 XXX.), the basals are represented as separated by small downward extensions of the 



