332 REPORT OF COMMISSIONER OF FISH AND FISHERIES. — [628] 
emarginate in the center, bat not deeply fissured. In contraction the 
body is broader posteriorly. Dorsal surface a little convex; lower side 
side flat. Acetabulum round, rather small, about half the diameter 
of the body in the contracted state, but nearly as broad when the body 
is fully extended. The intestine shows through the integument dis- 
tinctly ; it is slender, and makes about seven turns or folds. Color 
pale yellow, with minute white specks beneath and on the upper sur- 
face anteriorly, giving it a boary appearance; middle of the dorsal 
surface irregularly marked with flake-white; laterally reticulated with 
fine white lines. 
Length in extension, 25"; breadth, 4™™; in partial contraction, 
iS™™ long; 5™™ to 6™ wide. i 
New Haven, parasitic in the branchial cavity of the round clam ( Venus 
mercenaria), October, 1871. Philadelphia, in the same clam (Leidy). 
GYMNOCOPA. 
TOMOPTERIS, species undetermined. (p. 453.) 
Young specimens of a species of this genus were taken in the even- 
ing in Vineyard Sound. They are too immature for accurate identifica- 
tion. 
A large and fine species of Tomopteris was taken by Mr. S. I. Smith, 
in Eastport harbor, in July, 1872. This was about 40™ in length. An 
excellent drawing of it was made by Mr. Emerton from the living 
specimens. It is, perhaps, the adult state of the Viueyard Sound 
species. 
- CH.ETOGNATHA. 
SAGITTA ELEGANS Verrill, sp. nov. (p. 440.) 
Body slender, thickest in the middle, tapering slightly toward both 
ends. Head somewhat broader than the neck, and about equal to the 
body where thickest, slightly oblong, a little longer than broad, obtuse, . 
rounded in front or sub-truncate, sometimes with a slightly prominent 
small central lobe or papilla; the anterior part of the head rises into a, 
crest-like median lobe considerably higher than the posterior part; 
ocelli two, minute, widely separated, on the posterior half of the head; 
the anterior lateral borders of the head are slightly crenulated. The 
fascicles of sete or spinules on the sides of the head each contain about 
eight sete, which are considerably curved, with acute tips, and reach 
as far as the anterior border of the head. Caudal fin ovate; its poste- 
rior edge broadly rounded. The posterior lateral fins commence just 
in advance of the ovaries, and extend back considerably beyond them , 
so as to leave a naked space somewhat less than their length between 
their posterior ends and the caudal fin; on this naked part, just in ad- 
vance of the caudal fin, are two small, low, lateral papillae connected 
with the male organs; two other smaller papill are situated at about 
the posterior third of the lateral fins. The median lateral fins are about 
equal in length to the posterior ones, and separated from them by a 
