324 THE VOYAGE OF H.M.S. CHALLENGER. 



Pentacrimis decoriis and Pentacrinus miilleri in the Caribbean Sea. There are ncarlj- 

 always five or six internodal joints in the stem, and I have only noticed two cases of an 

 arm-division consisting of more than two joints united by syzygy. One has three joints, of 

 which the first two form a syzygy, and in the other there are four, those of each pair being- 

 united by syzygy. In the arms, however, the position of the syzygies, after that at the 

 base, is exceedingly variable. But this is always the case in the few species of Penta- 

 crinus which have syzygies in the arms, the contrast between them and the Comatulse 

 being very striking in this respect. 



Pentacrinus alternicirrus appears to inhabit moderately deep water, the depths at the 

 two Stations from which it is recorded being respectively 500 and 600 fathoms ; while 

 at the doubtful Station 210 the depth was 375 fathoms. Five of the individuals dredged 

 at Station 214 (Meangis Islands) were infested with encysted Myzostomas, as were also 

 many of the Comatulse. In one specimen no less than eight arms bore more or less 

 perfect cysts of Myzostoma pentacrini, von Graff, two of them having two cysts a short 

 distance apart. In other cases the cysts were principally formed in the skeleton of the 

 pinnules by Myzostoma deformator, von Grafi",^ as sho-s\Ti in PL XXVII. figs. 7 and 8 ; 

 while figs. 9 and 1 represent cysts formed in the substance of the arm. 



6. Pentacrimis naresianus, n. sp. (PI. XXVII. figs. 11-13 ; Pis. XXVIII.-XXX.). 



Dimerisions. 



Total length of largest specimen, stem broken at thirtieth node, 



Length of this stem, .... 



Diameter of stem, ..... 



Longest cirrus (thirty-five joints). 



Diameter of calyx, ..... 



Length of arm (eighty joints), 



Length of first pinnule (twelve joints). 



Length of pinnule from middle of arm (twenty-two joints), 



54-00 cm. 



38-00 „ 



5-00 mm. 



25-00 „ 



7-75 „ 



150-00 „ 



8-.^0 „ 



24-00 „ 



Stem long and smooth, of a rounded pentagonal or circular form. Eight to eighteen 

 (usually al>out ten or twelve) internodal joints wiih but slightly crenulated edges. 

 Nodal joints high, not projecting outwards at the angles, but deeply hoUowed by the 

 cirrus-sockets, which have nearly cu-cular facets and terminate far below the upper edges 

 of the nodal joints. lufra-nodals deeply grooved to receive the cirrus-bases, so that 

 the sockets appear to have pyriform do-wnward extensions. Cirri moderately slender, 

 of thirty to thirty -five tolerably uniform joints, all but the lowest of which have one 

 or two blunt projections on the dorsal edge. Lowest limit of the interarticular pores 

 between the fifth and eidith nodes. 



o 



Basals small, triangular or pentagonal, sometimes meeting laterally and sometimes 



1 Zool. Chall. Exp., part xxvii. pp. C2-C6, 1884. 



