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8. On two New Genera or ACEPHALOtsS MOLLUSKS. 
By Henry Apams, F.L.S. 
My attention having been lately directed to the genera Cultellus 
and Macoma, the former belonging to the Solenide, aud the latter 
to the Tellinide, both families of Acephalous Mollusca, it may, I 
think, be interesting to point out two species hitherto included in 
those genera, viz. Cultellus cultellus and Macoma bruguieri, which 
are so aberrant in their characters as to render it desirable that they 
should be constituted the types of distinct groups. The former may 
be considered a genus, for which I would propose the name Ensz- 
eulus, and the latter a subgenus of Macoma, and be distinguished 
under the name Macalia. 
Genus Ensicutvus, H. Adams. 
Testa tenuis, transverse elongata, arcuata, utraque extremitate 
votundata et hiante ; umbonibus subanterioribus, interne costa 
brevi curvataque jirmatis. Cardo in dextra valva duobus den- 
tibus, in sinistra valva tribus dentibus instructus. Anterior 
impressio muscularis subtrigonalis ; sinus pallialis brevis et 
latus. 
E. cu.retuvs, Linn. 
Shell thin, transversely elongated, arcuated, rounded and gaping 
at each end ; beaks sub-anterior, strengthened internally by a short 
curved rib. Hinge composed of two teeth in the right, and three 
in the left valve. Anterior muscular impression subtrigonal ; pallial 
sinus short, wide. 
This genus is most nearly allied to Cultellus, but differs from it in its 
arcuated and more elongated and parallel form, and in the strength- 
ening callus of the umbo being short and curved. 
The genus Macoma, I would observe, will probably, when an op- 
portunity of examining the animal of Gastrana shall occur, be found, 
as pointed out by Mr. Clark in his ‘ British Mollusca,’ to have closer 
relations with Gastrana than with Tellina; and the chief peculiarity 
of Macalia, as distinguishing it from Macoma proper,—viz. the large 
size and strength of the hinge-teeth, which are strikingly similar to 
those of Gastrana,—tends to confirm this opinion. The general form 
of Macalia, however, which is subrotundate and compressed, toge- 
ther with the solidity of the shell, prevents its being included in that 
genus. The entire absence of lateral teeth serves to distinguish the 
species of Macoma and Gastrana from the Telline. 
I may take this opportunity of referring to a paper by Mr. Pease 
lately read before the Society, in which he describes a new Vevilla 
from the Sandwich Islands under the name of V. nigro-fusca ; and, 
as the species hitherto recorded of the genus are few in number, 
this addition is interesting. The shell in question, however, differs 
from the typical species, in the spire being acuminate, and in the 
aperture being somewhat contracted or narrowed, and should, I 
think, be regarded as the type of a subgenus, which might be named 
Usilla. 
No. 440.—Proceepines or THE Zoouoeicat Socrety. 
