MUSEUM OF COMPARATIVE ZOOLOGY. 245 
Arca (Barbatia) pteroessa E. A. Smith seems very similar externally to our 
shell, but the hinge is different and the shell more produced behind ; the 
manner in which the black ligament is placed would seem to be similar in 
both. 
An allied species with an outline almost precisely similar to A. culebrensis 
Smith (Chall. Rep., pl. xvii. fig. 9 a) was obtained (a single valve) N. W. of 
the N..W. end of Cuba in 80 fms. by the U. S. steamer “ Albatross” in 1885. 
It has a hinge much like that of J. asperula, but its external surface is 
entirely different; there are numerous concentric grooves, with wider inter- 
spaces covered everywhere with an oblique shagreened ornamentation ; beside 
this there are obsolete radiating series of minute scales, probably stronger in 
some specimens, and on and behind the ridge from the umbo to the posterior 
angle of the margin are four well defined and two or three obsolete nodulous 
radii. The valve is about six millimeters long and quite inflated; the um- 
bones must nearly touch in perfect specimens, as the area is extremely narrow 
and the beak well developed. It may take the name of M. sagrinata. 
Professor Verrill’s Arca profundicola, though not very characteristically 
figured, is, from a typical specimen, more finely striated, the lower posterior 
region less patulous and its hinge margin not so high. The front teeth are 
more, and the hind teeth less, oblique than in Macrodon. It may be observed 
that the gap between Macrodon and certain forms of Barbatia is not very wide. 
Famity NUCULIDA. 
Genus NUCULA Lamarck. 
Nucula Lamarck, Prodrome d’une Nouv. cl. des Coquilles, p. 87, no. 104, 1799. 
Type Arca nucleus, L. 
Nuculana Link, Beschr. Rost. Samml., p. 155, 1807. 
I take this opportunity of mentioning, for students who cannot get access to 
the rare work of Link, that his Nuculana is an exact synonym of Nucula 
Lamarck, and was intended merely as a modification of that word; while the 
diagnosis, “shell smooth, closed all round,” will not apply to the group sepa- 
rated by Schumacher, afterward, under the name of Leda. That the only 
species of the group in the collection was N. rostrata was merely an accident, 
and it was evidently not intended as a type, for it does not agree with his 
diagnosis, 
