REPORT ON THE HOLOTHURIOIDEA. 49 



degree of curvature is rather variable ; sometimes, though rarely, an arcuated arm pro- 

 jects from the middle of the convex side, sometimes its C-shape is changed into the 

 form of an S. 



Peniagone challenger), n. sp. (PI. IX. figs. 6-8). 



Body elongated, of almost equal breadth throughout, about five times as long as 

 broad, depressed posteriorly; its posterior flat extremity with an incision in its middle. 

 Mouth anterior, ventral. Anus posterior, dorsal. Tentacles of almost equal size ; their 

 discoidal, terminal part with small retractile processes. Pedicels eight or nine along 

 each side of the ventral surface ; the anterior half of that surface destitute of pedicels. 

 The dorsal surface having anteriorly an extension of the skin, constituting a long, broad, 

 flattened, obliquely transverse lobe, with two rather considerable projections in its upper 

 margin. Integument rather hard and rough, with numerous, crowded calcareous deposits, 

 composed of a slightly elongated central part, and two more or less curved spinose arms 

 diverging from each of its ends ; each arm with a spinose process, directed outwards ; the 

 length of the arms and processes extremelv variable. 



Colour in alcohol, light grey, inclining to violet. Length, about 65 mm. Breadth 

 about 13 mm. 



Habitat.— Station 158. March 7, 1874. Lat. 50° 1' S., long. 123° 4' E. Depth, 

 1800 fathoms; bottom temperature, # 3° C. ; globigerina ooze. Two specimens. 



As the above dimensions indicate, the body, being of equal breadth throughout, seems 

 very narrow in comparison to its length. It attains its greatest height a little behind 

 the tentacles and immediately in front of the large appendage, which divides the dorsal 

 surface into a posterior part, which is slightly convex and gradually approaches the ventral 

 surface posteriorly, and into an anterior, extremely convex part. The large anus is situated 

 on the dorsal surface a little in front of the incision. The dorsal appendage, measuring 

 about 22 mm. in length and about 12 mm. in breadth at the base, crosses obliquely from 

 one side of the dorsal surface to the other, so that while the base at the right side is 

 found at a distance of about 20 mm. from the anterior extremity of the body, this 

 distance at the left side, on the contrary, amounts only to about 1 1 mm. The upper edge 

 of the lobe is deeply emarginated so as to form two rather slender processes, 8 to 1 mm. 

 long, the right one being a little the larger. The tentacles, of which four are torn off, 

 appear to be of almost equal size ; their terminal part is large and discoidal, and of the 

 small retractile processes the two on the outer edge have the appearance of being the largest. 

 The five anterior pairs of pedicels are large in comparison to the posterior ones and 

 separated from each other at certain distances ; the seven remaining pedicels, which run 

 out from the flat, truncated posterior end of the body are small and directed back- 

 wards, very closely crowded, and disposed four on the right side of the above-mentioiird 

 incision, and three on the left. The calcareous deposits (PL XXXIII. fig. 16) vary 



(ZOOL. CHALL. EXP. PART XIII. 1881.) N 7 



