VAN NAME: COMPOUND ASCIDIANS. 
377 
large colony is from Station 2471 (X. lat. 44° 34', W. long. 5(3° 41' 4.3", 
218 fathoms, gray mud, sand, July 4, 1885). The species ranges, 
however, much farther south, as there are colonies from Station 2429 
(N. lat. 42° 55', W. long. 
50° 51', 471 fathoms, gray 
mud, June 23, 1885) ; from 
N. lat. 42° 53', W. long. 
59° 04', 100 to 150 fath- 
oms; and from Station 
2523 (N. lat. 41° 48', W. 
long. G5°44', 111 fathoms, 
sand, gravel, stones, July 
13, 1885). 
There are also two small 
colonies having somewhat 
fewer and less regular spicules (text-fig. 12) than the other specimens, 
so that the test is quite translucent, but apparently they are of this 
species. These are from the great depth of 1582 fathoms (Station 
2228, N. lat. 37° 25', W. long. 73° 06', brown mud, September 11, 
1884). This depth is more than double that of any previously 
recorded station for a species of this family. 
Text-fig. 12. — Leptoctinides faeroensis Bjerkan. 
Spicules from a colony from Station 2228 (N. lat. 
37° 2.5', W. long. 73° 06', 1582 fathoms). X 515. 
Genus Tetradidemnum Delia Valle, 1881. 
As already mentioned (p. 370), the writer believes that the species 
having an atrial languet should be removed from the genus Didemnum 
[Leptoclinum]. In two genera of this group, Polysyncraton Xott, 
1891, and Tetradidemnum Delia \ alle, 1881, the atrial languet is 
present. It seems best to continue to restrict Polysyncraton, as here- 
tofore, to forms having the testis divided into a considerable number 
(four to ten) of distinct parts. The writer has therefore provisionally 
referred the species described below to Tetradidemnum. The type 
of the genus, T. gif/as of the Mediterranean, was figured by Delia 
Valle (1881, pi. 5, fig. 47; pi. 7, fig. 69), but never described. Re- 
cently Delia Valle (1908) has claimed that Tetradidemnum should 
replace Didemnum Savigny, 1816, on the ground that Savigny did not 
sufficiently characterize his genus. With this view the writer does 
not agree, but believes that Tetrp,dideinnum is available as a name 
for that subdivision of Didemnum which contains Delia Valle's type 
