S58 



THE VOYAGE OF H.M.S. CHALLENGER. 



been the suppression of tlie second radial pinnule. As a matter of fact, however, it is 

 present on the epizygal of the second radial, which thus bears two pinnules, one on each 

 side. A similar instance of two pinnules on one joint also occurs in Metacrinus 

 cingulatus {ante, p. 349), and recalls the condition of certain Palseocrinoids. 



In the next ray to this one the fourth radial, which is a syzygial joint, is also the 

 axillary; and although the first and second radial pinnules are present as usual, the 

 axiUary epizygal bears a pinnule in addition to the two primary arms. This pinnule, 

 however, really belongs to one of the first distichal joints, which is much smaller than its 

 fellow^ and does not reach the outer edge of the arm at all. The consequence is that the 

 first pinnule of the primary arm is borne by its second and not by its first joint, as is 

 usually the case. 



Apart from these irregularities, the larger dry specimen of Metacrinus moseleyi 

 appears to be tolerably normal in its character. But the smaller individual is different. 

 The stem tapers downw^ards, being only 3 mm. Avide at the twenty-third node, but 

 rather over 4 mm. at the twelfth node. The arms too are much malformed by com- 

 mencing Myzostoma-cysts, either in the arm itself, or in the base of a pinnule, as shown 

 in PI. XLV. fig. 7. 



7. Metacrinus wyvillii, n. sp. (PL XL VII. figs. 1-5 ; PL XLVIIL). 



Dimensions. 



Length of stem to thirty- fourth node, 



Diameter of stem, ...... 



Longest cirrus (forty-five joints), .... 



Diameter of calyx, ...... 



Length of arm (ninety joints beyond palmar axiUary), 



Length of first distichal pinnule (fifteen joints), 



Length of first pinnule after palman axillary (sixteen joints), . 



Stem pentagonal and moderately robust. Five to eight (generally seven) internodal 

 joints, with more or less well defined horizontal ridges and slightly crenulated edges. 

 Nodal joints bluntly stellate, wdth large fiicets of variable shape which take up their 

 whole height, while the sockets extend on to both supra- and infra-nodal joints, especially 

 the latter. Cirri of forty to forty-five very uniform joints, the lowest of which are but 

 little wider than their successors. The lower cirri not specially shorter than the 

 upper. Interarticular pores extend down to the sixth or seventh node. 



Basals pentagonal, large and prominent, more or less sharply pointed lielow, some- 

 times being almost hexagonal. Radials usually six, with syzygies in the second and 

 fourth. The rays, which are somewhat closely set, divide three or very rarely four times, 

 giving nearly forty arms. These have about ninety joints above the palmar axillaries, 

 and are almost quite smooth dorsally, except in the terminal third. Primary arms of 



