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



This couclition recurs over a length of three iutemodes ou the remaining stem-fragment, 

 the sockets gradually becoming more and more obscured ; and at the lowest node the 

 incrustation seems to have completely overgrown the bases of the cirri, nothing appear- 

 ing to indicate their presence but minute irregular stumps. Fifty joints lower down 

 the stem terminates in a flattened expansion by which it was probably attached. The 

 abnormal condition of this stem is interesting from its resemblance to that presented by 

 a specimen of the fossil Millericrinus pratti, which I have described elsewhere.^ In 

 this case, however, the secondary deposit of limestone which is outside the uppermost 

 stem-joints is divided up into segments not corresponding \\T.th those enclosed by it. 



7. Petitacrmus hlakei, P. H. Carpenter (Pis. XXXI., XXXII. ; PI. XXXIII. 



figs. 1-3). 



1882. Fentaunnus hlakei, P. H. Carpenter, Bull Mus. Comp. Zool., vol. x. p. 172. 



Dimensions. 



Total length, ...... 



Longest stem, rounded off at twenty-fourth node, 

 Diameter of stem, ..... 

 Longest cirrus (twenty-nine joints), 

 Diameter of calyx, ..... 

 Length of arm (one hundred and tive joints), . 

 Length of pinnule on first distichal (eighteen joints), . 

 Length of pinnide from middle of arm (twentj' joints). 



27-5 cm. 



160-0 mm 



-I'O 



17-0 



6-0 



120-0 



9-0 



12-0 



Stem slender and smooth, with a rounded pentagonal outline ; five to seven inter- 

 nodal joints with distinctly crenulated edges. Nodal joints high, not projecting out- 

 wards between the cirrus-facets, which are comparatively small and cii'cular, and do 

 not nearly reach their upper edge. Infra-nodals more or less grooved to receive the 

 cirrus-bases, so that the sockets appear to have pyriform downward extensions of 

 variable size. Cirri small and slender, of twenty -five to thirty joints, the first six of 

 which are quite short, and the remainder squarish ^^ith a tolerably smooth dorsal edge. 

 Terminal claw small, with no opposing spine. Lowest limit of the interarticular pores 

 between the sixth and tenth nodes. 



Basals small, triangular, and more or less rounded, well separated laterally Ijy the 

 lowest parts of the rather high radials. The rays and their subdivisions moderately close, 

 without any iutei'vening perisome, but scarcely flattened at all except just on the lower 

 brachials. The two outer radials and lowest distichals respectively united by bifaseial 

 articulation. The third radials and the second distichals project backwards into the middle 

 of the preceding joints, their proximal surfaces being somewhat deeply hollowed from side 

 to side, and slanting downwards and backwards. About twenty arms, usually only 



1 Qimrt. Joarn, Col Soc, vol. x.\xviii. p. 33, pi. i. tig. 21. 



