REPORT ON THE HOLOTHURIOIDEA. 17 



The body is of an almost cylindrical form, but tapers slightly towards each extremity, 

 the thickness being not quite the same throughout. The mouth and tentacles are almost 

 terminal. The anus is large, dorsal, and situated near the posterior end of the body. 

 The tentacles are doubtless ten in number, though in the only specimen existing in the 

 collection only five are left ; the rest have apparently been torn off. As their terminal 

 part is more or less contracted, it is impossible to state correctly the form or number 

 of the processes. Like the preceding species, this one is destitute of pedicels on the 

 anterior part of the body, the first pair arising about 70 or 75 mm. behind the ten- 

 tacles. The first five pairs of pedicels have a cylindrical form with the ends slightly 

 enlarged ; the posterior parts are narrower and a little longer. As in Parelpidia 

 elongata, the spaces between the different pairs decrease backwards, so that the four 

 hindmost pairs are close together at the posterior extremity of the body. The dorsal 

 surface is furnished with four very small rudimentary processes, arranged in pairs, two on 

 each ambulacrum, the first pair being situated 20 mm. and the posterior pairs about 

 45 mm. behind the tentacles. The perisoma is quite transparent and very thin, so that 

 the five broad yellowish muscular bands are distinctly visible through it ; its surface is 

 scattered over externally with very small papillae, each containing a calcareous deposit, 

 evidently of almost the same shape as in Parelpidia elongata. Unfortunately, those 

 deposits are quite dissolved, and it is only by treating the skin with hsematoxylin or 

 carmine that their outlines can be distinguished. 



The alimentary canal is narrow ; it descends to the anal extremity of the body, where 

 it turns upon itself and forms a small circumvolution. Throughout the whole of its 

 course, the alimentary canal is attached to the wall of the body by larger or smaller 

 bands. The cloaca is of inconsiderable dimensions. The polian vesicles, ventral and two 

 in number, are 1 2 mm. long. The madreporic canal is rather thick and, after penetrating 

 the perisoma, communicates with the exterior by a pore situated not very far behind 

 the tentacles. I have not been able to observe more than a single pore, although 

 possibly there might be several. The reproductive organ is unusually long, nearly 

 the lenoth of the body, consisting of two very slender tubes of almost equal thickness 

 throuo-hout and divided posteriorly into thread-like branches. The tubes carry here and 

 there thin bundles of such branches, and anteriorly, where both of them join and form 

 a wide sack-like extension, there are several other small, very close-set bundles of slightly 

 thicker branches. The whole reproductive organ is therefore very slender, almost fili- 

 form. The two species of this genus are evidently nearly allied. The transparency of 

 the integument and its extreme thinness, the length and slenderness of the reproductive 

 organ, the number of the processes, and especially the shape of the pedicels, distinguish 

 this species from the preceding one. 



(ZOOL. CHALL. EXP. — PART XIII. 1881.) N 3 



