EEPORT ON THE HOLOTHIJRIOIDEA. 
89 
valves, these openings being surrounded by cii’cles of numerous scales which seem to 
decrease towards the openings themselves, so that the number of scales between the 
mouth and the anus was greater. Only in very small specimens (about 15 mm.) of 
Psolus squamatus have I observed a more or less regular arrangement of larger oral and 
smaller anal valves, but I have never observed this in Psolus fabricii, though I have 
examined much smaller individuals of this species. Moreover, there is a great 
difference in the arrangement of the pedicels, when comparing specimens of about the 
same size. As has been pointed out, Psolus antarcticiis has two rows of pedicels, while 
equally large specimens of Psolus squamatus (about 50 mm. long) always have three 
rows. Even the odd ambulacrum in the northern form seems to have more pedicels. 
The deposits in the sole of Psolus squamatus resemble those in the same region of 
Psolus antarcticus, but they often seem to be devoid of knobs or other processes. 
The specimen brought home from Station 320 is very small, 13 mm. long, and has 
the oral and anal valves very regularly arranged. Its pedicels are disposed in two 
rows round the sole, which seems to be completely devoid of deposits. The scales are 
comparatively large, so that only four are situated between the oral and anal valves. 
The surface of the scales is nearly smooth. Having seen only a single specimen, I 
could not make any detailed examination, but it seems probable that it belongs to the 
species in question. 
Psolus squamatus, Diiben and Koren, 1844 (var. ?) (PL XV. figs. 1, 2 ; PI. VI. fig., 2). 
Habitat. — Station 307, January 4, 1876 ; lat. 49° 24' 30" S., long. 74° 23' 30" W.; 
depth, 140 fathoms; blue mud; twm specimens. Station 308, January 5, 1876; lat. 
50° 8' 30" S., long. 74° 41' W.; depth, 175 fathoms ; blue mud ; two specimens. Station 
311, January 11, 1876; lat. 52° 45' 30" S., long. 73° 46', W. ; depth, 245 fathoms; 
bottom temperature, 46°'0 ; blue mud ; several specimens. 
The four individuals brought home from Stations 307 and 308 are rather large, 
varying from 50 to 60 mm. in length. If not identical, they cannot be considered as 
anything more than varieties of the northern form. They even seem to combine this 
form with Psolus antarcticus. A double row of pedicels surrounds the sole, those in 
the outer row being situated on the inner side of the margin. Strangely enough, one 
of the specimens obtained at Station 307 possesses pedicels on the odd ambulacrum, and 
these form a simple row at the middle of the body but an alternating double row 
posteriorly and anteriorly. Considering the fact that the other specimens are in want 
of the middle row of pedicels, and having regard to the general appearance of the body, 
it is most probable that this peculiarity may be referred to an individual deAuation. 
The scales bear small rounded granules which occur especially round the free margin ; 
the oral aperture is closed by five larger triangular scales, alternating with and partly 
(ZOOL. CHALL. EXP. — PART XXXIX. 1885.) Ql 
