MUSEUM OF COMPARATIVE ZOOLOGY. 299 
posteriorly directed groove or fossette; surface smooth or concentrically sculp- 
tured. Type Newra adunca Gould. 
This is equivalent to Smith’s Section F. It would include, according to his 
description, Neera Braziert Smith. I have compared specimens of N. adunca 
Gould, received from Drs. Arthur Adams and Gould, which agree perfectly with 
Adams’s description of Leiomya. The cardinal tooth in the right valve is bifid 
at the tip and very small; hence Adams in his diagnosis ascribed two cardinal 
teeth to this valve, but I think they should be counted as one. 
What the shell is, described by my friend Smith as type of his Section J, 
under the name of Neera adunca Gould, I do not know. He has evidently 
been misled by a wrongly named shell. It is certainly an entirely different 
species and section from Leiomya. It has no cardinal teeth, a small central 
fossette, a small thickish anterior and posterior lateral in the right valve, and 
a similar anterior lateral (only) in the left valve; the surface is finely ridged. 
It appears to be the only species with these characters, and I would sug- 
gest the name of Vulcanomya Smithii for it in default of any other legitimate 
designation. Its external characters and size closely resemble those of the 
genuine N. adunca Gld., which would account for the error, in the absence 
of types. 
Mr. Smith kindly informs me that he has re-examined the specimens, and 
finds nothing to change in his description of them. They were received at the 
British Museum with Gould’s name attached by some one unknown, 
Section PLECTODON Carpenter. 
Plectodon Carpenter (Suppl. Rep. Brit. As., p. 638, Aug. 1864) is closely re- 
lated to Lezomya. It differs in the insertion of the cartilage behind and under 
the beaks, instead of on,the hinge-margin or in a fossette; in having, rather than 
a true tooth upon the margin, a tooth-like prominence formed by the spiral 
twisting under the b iks of the hinge-margin itself, upon and over which, in 
P. scaber, there is a Jainute external ligament; lastly, in Plectodon there is a 
granulated surface much as in Poromya. The pallial sinus appears to be about 
the same in both, and the tips of the siphons are protected, in both groups, 
as in Schizotherus, by a leathery ring, flattened and broadened at the sides. 
Until recently only two right valves of Plectodon were known, but in 1873 I 
dredged at Catalina Island, California, in 16 fms., mud, some half a dozen 
living specimens, which have enabled me to make a careful comparison with 
my Neera granulata. There can be no donbt of their generic identity, and 
even considered as species they are very similar, the intwisting of the margin 
being less marked in granulata and the supposed external ligament obsolete, 
I regard Plectodon, therefore, as a mere section of Leiomya, which might also 
include Rhinoclama, which is of about equal value with Plectodon, 
