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



out the five muscular bauds. Exteriorly, the integument is provided with very small 

 papillae, each of them containing a four-armed calcareous deposit (PI. XXXII. fig. 1G), 

 the form of which has been already described in the character of the genus. The four 

 curved arms of that deposit are directed towards the base of each papilla, and the 

 long central process towards the top. The arms as well as the process are more or less 

 spinose, though it is impossible to decide to what degree, several calcareous bodies having 

 been thoroughly dissolved and the rest considerably deformed, the alcohol, in which 

 this animal as well as some others had been preserved, probably having become acid. 

 The length of the arms of those calcareous bodies is about - 12 mm. The end of the 

 pedicels contains a number of larger and smaller unbranched spicula and four-armed 

 irregular bodies (PL XXXII. fig. 17). 



As usual in this family the calcareous ring (PI. XXXVII. fig. 2) is composed of five 

 radial pieces or spicula, as I prefer to call them, which, being separated from one 

 another in this species, do not form a complete ring round the gullet. Each spiculum con- 

 sists of a short central part, from, which radiate on each side ten to fourteen slender rods, 

 0"8 mm. long, slightly arcuated, and towards the end widened, flattened, and more or less 

 branched. In the layer of connective tissue round the calcareous ring is a quantity of 

 more or less irregular four-armed bodies, resembling those of the pedicels. Two ventral 

 polian vesicles are to be observed, one on each side, and two other rudimentary prolonga- 

 tions are given off from the circular vessel. The madreporic canal seems to be destitute of 

 calcareous deposits, and it has not been possible to determine whether it pierces the wall of 

 the body or not. The reproductive organ, only 25 or 30 mm. long, is composed of two 

 branches, each enlarged posteriorly and divided into a number of small bundles of caecal 

 branches. The anterior part of the organ also carries at its sides some small, thin 

 bundles of the same shape. On the nerve ring are to be observed small auditory vesicles 

 containing thirty or forty otoliths of the usual ovate form, Avith one end abruptly broken 

 off, and with three to four concentric layers ; the size of these otoliths varies from 

 0-21 to 0'04 mm. in length. 



Parelpidia cylindrica, n. sp. (PI. I. figs. 1, 2). 



Mouth anterior, terminal. Anus posterior, dorsal. Tentacles bearing on their terminal 

 part small retractile processes. Pedicels nine along each side of the ventral surface, of 

 almost equal size, the posterior pairs being a little longer but thinner. The dorsal 

 surface with two pairs of very small rudimentary processes on its anterior part. 



Colour in alcohol, light grey. Length, about 185 or 190 mm. Breadth, about 36 or 

 70 mm. 



Habitat— Station 298. November 17, 1875. Lat. 34° 7' S., long. 73° 56' W. 

 Depth, 2225 fathoms; bottom temperature, l - 3° C. ; grey mud. One incomplete 

 specimen. 



