390 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
In the opinion of the writer, they are the ones that should constitute 
the genus Diplosomoides, but D. dubium and D. flcvvescens should be 
removed from Diplosomoides and placed with Verrill's species in the 
genus Lissoclinum, a genus which bears exactly the same relation to 
Diplosomoides that Polysyncraton bears to Didemnum [Leptoclinum]. 
The same distinctions that have led to the recognition of Polysyncraton 
justify the recognition of Lissoclinum. Its characters are as follows: 
Cotony variable in form, flat and incrusting or of considerable height. 
Common test often with extensive cavities. Calcareous spicules gen- 
erally present. Branchial aperture six-lobed; atrial aperture with 
a languet. Four rows of stigmata. Stomach smooth-walled. Testis 
divided completely or incompletely into four or more parts. Sperm 
duct not coiled about the testis. 
In this genus, as in the other genera of this family in which the sperm 
duct is not spirally coiled, viz., Leptoclinum [Diplosoma] and Diplo- 
somoides, and also in Echinoclinuin, the writer has been unable to find 
any trace of the branching tubular gland surrounding the intestine, 
while in those members of the family in which the sperm duct is coiled, 
viz., Didemnum [Leptoclinum], Leptoclinides, Didemnopsis, Tridi- 
demnum [Didemnum], Tetradidemnum, and Polysyncraton, it is 
conspicuous in any fairly well preserved material, consisting of a few 
(often only three or four) thin-walled tapering tubules without enlarged 
bulbs at the ends, which clasp the ascending part of the intestine. At 
their proximal ends they unite, and discharge into the intestine beyond 
the stomach by a common duct. 
In two (Didemnopsis, Leptoclinides) of the last-mentioned group of 
genera, the writer has been able to distinguish clearly the dorsal 
languets, which are not borne on the median dorsal vessel, but on the 
transverse vessels of the left side of the branchial sac at some distance 
from the median dorsal vessel. In Lissoclinum, and as far as he has 
been able to distinguish them in other genera of the Leptoclinum 
[Diplosoma] section of the family, they are apparently borne on, or at 
least close to, the median dorsal vessel. 
Lissoclinum aureum W-rrill. 
Text-figs. 18, 19, 20; PI. 39, figs. 11, 12, 16, 17. 
1871. Lissoclinum aureum Verrill, Amer. Journ. Sci., ser. 3, vol. 1, p. 444, 
fia;. 26. 
