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



Elpidia willemoesi, n. sp. (PL VIII. figs. 2, 3). 



Body elongated, of almost equal breadth throughout, about twice and a half as long as 

 broad, considerably depressed backwards, and the posterior very flat extremity with an in- 

 cision in its middle. Mouth anterior, ventral. Anus posterior, dorsal. Tentacles large, of 

 almost equal size, some of the ventral ones a little smaller than the others ; their terminal 

 part with retractile processes. The dorsal surface with three large, rather short, lobe- 

 like processes, arranged in a transverse row at its foremost part, the middle one larger 

 than the others, and with one or two very small, rudimentary processes on each ambula- 

 crum a little behind the former ones. Pedicels ten, all along each side of the ventral 

 surface, rather large, the hindmost pairs a little smaller. Integument thin, transparent, 

 with two sorts of calcareous deposits numerous : large four-armed bodies, each arm slightly 

 curved, and with numerous long spines and spinose processes ; smaller ones with the 

 arms less spinose, but more arcuated, and with two to four rather long, spinose processes, 

 directed outwards, or with only one central process. 



Colour in alcohol, light grey. Length, about 85 to 90 mm. Breadth, about 35 mm. 



Habitat.— Station 156. February 26, 1874. Lat. 62° 25' S., long. 95° 44' E. Depth, 

 1975 fathoms; diatom ooze. One almost complete and three incomplete specimens. 



The body is more or less distinctly elongated and the anterior part, in individuals 

 preserved in alcohol, is considerably narrower than the posterior. The ventral sur- 

 face is almost flat, and the back sbghtly convex, the height of the body being thus not 

 very considerable ; the greatest height is at its middle and anterior part. Posteriorly, 

 the dorsal surface gradually approaches the ventral surface, so that the posterior obtusely 

 rounded, almost truncated, extremity of the body is rather flattened ; it is incised in 

 its middle, so that it gives the impression of being bilobed. The anterior part of 

 the body terminates in three short, obtusely triangular processes or lobes, disposed 

 in a transverse row, and having their bases close to each other ; the middle process 

 is at its base several times broader than the other two. The body-wall surround- 

 ing those processes is thickened and projects from the mouth, which thus acquires 

 a thoroughly ventral position. In the single uninjured specimen we have had at our 

 disposal, not only the tentacles, but also a neck-like portion of the body, support- 

 ing them, protrudes below the ventral surface, forming thus a distinct angle with 

 it. In a thoroughly extended state it seems probable that the animal might change, 

 in some degree, the position of this neck-part, so as to stretch it forwards, possibly 

 beyond the three dorsal processes, which, instead of being directed forwards, ought to be 

 turned more upwards. The anus is situated on the dorsal surface immediately in front 

 of the incision in the posterior extremity of the body. The tentacles are of rather incon- 

 siderable size, some ventral ones being a little smaller than the others. Their terminal 

 parts are, as usual, mostly retracted, and bear a number of retractile processes, which, 

 especially towards their extremities, are provided with very small brownish projections, 



