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



Colour in alcohol, light reddish violet. Length, about 150 mm. Breadth, about 

 45 mm. 



Habitat.— Station V. January 28, 1873. Lat. 35° 47' N., long. 8° 23' W. Depth, 

 1090 fathoms ; bottom temperature, 3"1° C. ; mud. One individual Station 300. 

 December 17, 1875. Lat. 33° 42' S., long. 78° 18' W. Depth, 1375 fathoms ; bottom 

 temperature, 1'5° C. ; globigerina ooze. Two specimens. 



The above diagnosis as well as the following description are taken from the indi- 

 vidual, obtained at Station V. At the end of this description, an account will be 

 added of the differences which distinguish the specimens from Station 300. The body is 

 nearly of an equal breadth throughout or decreases slightly posteriorly, and has its ex- 

 tremities equally truncated and rounded ; it is remarkable for its great thinness, the dorsal 

 and ventral surfaces being only slightly convex. The flat brim is of considerable breadth 

 round the anterior and posterior extremities of the body, its edge being undulated, and 

 as if it were lobed anteriorly. The mouth and anus are situated on the ventral surface, 

 the former about 15 mm. from its anterior extremity, and the latter 7 to 10 mm. from 

 the posterior. The eighteen retractile tentacles attain about the same dimensions ; their 

 dilated terminal part is contracted, but presents some small processes, which are retracted 

 and seem to be placed round the edge. 



The processes of the dorsal surface present a conical form, and are not capable of 

 being retracted ; the three first pairs are situated anteriorly and are very small, only 

 from 3 to 5 mm. long ; the fourth pair, on the contrary, is considerably larger, its 

 processes measuring up to 15 mm. in length and 9 to 10 mm. in diameter at the base. 

 The first pair is situated at a distance of 35 to 40 mm. from the anterior extremity of 

 the body, while the fourth is placed 55 to 60 mm. from that extremity. The large, 

 azygous, lobe-like appendage has a transverse position, crossing the odd interambulacrum 

 about 45 mm. in front of the posterior end of the body ; it reaches 40 mm. in length 

 and its breadth at the base, measuring 16 to 18 mm., is considerably greater than its 

 thickness. The appendage has its top rounded and is penetrated by two wide canals, which 

 are in connection with the dorsal ambulacra. The pedicels or rather processes, which 

 shoot out from the margin of the foremost part of the brim belong doubtless to the dorsal 

 ambulacra ; from want of materials it has been impossible to make a closer examination 

 of it, but in other forms, which are closely allied to this species, I have found that to be 

 the case, and it probably should be common to the whole family. The pedicels of the 

 odd ambulacrum are disposed in two alternating rows, thirty-one in the left and thirty- 

 five in the right one, and are small and retractile ; the foremost part of that ambulacrum 

 is naked. The pedicels of the lateral ambulacra of the ventral surface are arranged in 

 a single row round the edge of the brim, and are small, retractile, and of a conical form, 

 and often hardly discernible. The perisoma is thin and more or less transparent. The 

 deposits of the ventral integument (PL XXXV. fig. 6) are partly made up of more or less 



