THE NAUTILUS. 23 



are hard to understand, and the meaning of which can only be 

 guessed. The latter were referred to by subsequent writers by the 

 mysterious words that there are " anatomical " or " histological " dif- 

 ferences. My own investigations have convinced me that all ana- 

 tomical or histological elements in the gill-structure of A. complan- 

 ata are essentially the same as in A. cygnea, the only actual differ- 

 ence being a slighter development of the interlamellar tissue in A. 

 complanata. And further, the shape of the glochidium is indeed 

 slightly different, that of A. cygnea being a little larger, and higher 

 in proportion to length. For the rest, A. complanata is absolutely 

 like A- cygnea) and the general shape of the shell, chiefly the con- 

 formation of the beaks and their sculpture, indicates clearly that A. 

 complanata is not only a true Anodonta, but also belongs to the same 

 group of the genus, of which A. cygnea is the type (as distinguished, 

 for instance, from the North American group of A. grandis). The 

 very slight differences in the anatomy alluded to above, and in the 

 glochidium, cannot be regarded as of more than specific value. 

 Pseudanodonta, consequently, is a synonym of Anodonta, and I must 

 confess that I rarely have come across a more useless and superfluous 

 genus. 



I hope to find occasion, in the future, to give a more detailed and 

 illustrated account of the European forms discussed here, and very 

 likely shall do so in connection with my studies of the soft parts of 

 a number of North American forms, in which I am now engaged. 



PUBLICATIONS RECEIVED. 



THE RECENT AND FOSSIL MOLLUSKS OF THE GENUS CERITHI- 

 OPSIS FROM THE WEST COAST OF AMERICA. By Paul Bartsch 

 (Proc. U. S. Nat. Mus., vol. 40, May 8, 1911). Former work on 

 the forms is reviewed, followed by a classification of the species into 

 the subgenera Cerithiopsis proper, Cerithiopsina, Cerithiopsidella and 

 Ceritkiopsida, based upon characters of the embryonic and early 

 neanic whorls. Of 44 species known from the west coast of North 

 and South America, five occur only fossil, and 25 are described as 

 new. All the species are illustrated by photographic figures. It is 

 an important work on a difficult and hitherto little-known genus. 



NEW SPECIES OF SHELLS FROM BERMUDA. By W. H. Dall 



