2 BULLETIN OF THE 



though synonymous with each other ; but they should not, as M. Cross© 

 observes in a letter on the subject, be united until clear proofs are shown 

 of identity, and therefore I have proposed for the present form a pro- 

 visional varietal name,"which may serve to distinguish it until the question 

 is settled by the comparison of specimens. My largest specimen meas- 

 ured .26 inches wide by .18 long. 



Small as is this species, it is considerably larger than those of the 

 Mediterranean, and it was with much interest that I submitted it to an 

 anatomical examination. 



I have not met with much success among these small species in the use 

 of acid in dissolving away the shell from the animal, and have been prin- 

 cipally obliged to work with specimens forcibly removed from their shells, 

 — a process which is not calculated to present the parts in the best con- 

 dition. Nevertheless, I have been able to determine some points of interest 

 in a satisfactory manner. 



The brachia in this and the other species of the genus are arranged 

 around the edge of a broad membrane, which covers the concavity of the 

 shell, like a drumhead. The hoop of the drum is represented by the 

 apophyses. The brachia differ from the same organs in the Terebratulince 

 in being arranged in a single series instead of a double one. Of this there 

 can be no doubt, it is very evident upon a casual inspection, and is entirely 

 confirmed by careful dissections. In this species the drumhead membrane 

 is divided into two lobes by the septum. The edges of these lobes are 

 fringed with the brachia. The latter, in the alcoholic specimens, show 

 distinct transverse markings. They are usually curled up in front and on 

 each side, while those which are situated behind the mouth are longer than 

 the others, and usually lie smoothly over them, extending forward without 

 any marked curve, pointing toward the anterior margin of the shell, and 

 extending clear over the central membrane, even beyond the posterior 

 edge of the septum. The brachia are covered with an epithelium fur- 

 nished with cilia, are tubular, and communicate with a series of brachial 

 channels, which did not appear to differ from those of Waldheimia as de- 

 scribed by Hancock, as far as I was able to discover. The great brachial 

 canal was rendered conspicuous by a band of cartilaginous substance which 

 seemed to form its external covering, or rather beneath Avhich it was 

 situated, and which was longitudinally striated. The external edge of the 

 membranes, between which the apophyses were formed, was directly at- 

 tached to the pallial lobes at the points where the apophyses are attached 

 to the muscular disks of attachment already described. On either side of 

 this attachment, however, was a kind of pocket, opening externally, where 

 the brachial and pallial membranes did not coalesce ; and, there being one 

 on each side of the point of union, there were consequently four in all, 



