106 THE NAUTILUS. 



Atlantic coast : Petricola lapicida Gnil., P. typica Jonas, P. pholadi- 

 formis Say, and P. dactylus, Sovvb. In referring to the latter Dr. 

 Dall gives the following interesting note : " The curious little shell 

 named in 1872 by Verrill Gastranella tumida, is certainly a Petri- 

 cola, and I suspect it to be the young of P. daetylus, which has 

 when very young and fresh a purplish tinge on the umbones in some 

 individuals. The tinge is precisely the same in both. Carpenter 

 similarly took the nepionic young of P. denticulata Sowerby for a 

 Psep/tis and described it under the specific name of tellimyedis. This 

 was the more excusable, since the fry are brightly colored with 

 orange and purple, while the adult and adolescent stages of the 

 Petricolaria are pure white. I have a series showing the latter with 

 its purple umbones strongly contrasting with the white valves, but 

 this condition lusts only a short time, the color fading entirely out in 

 most specimens before they attain full growth." 



A most excellent synopsis of the Cardiidae is followed by a review 

 of the species, of which 28 are new. Oardium fiuridanum Heilp, is 

 a syn. of G. emmonsi Conr.; for C. magnum Born (not Linne), G. 

 robustum Solander is adopted. Gardium bullatum of authors as of 

 Linne' not of Morch, becomes C. spinosum Meuschen ; G. setni- 

 sulcatum Gray, has priority over G. ringiculum Sowb., and C. Petiti- 

 anum Orb., G. (Lavicardium) serratum L., and G. lozvigeitum Lam., 

 are considered synonymous. 



A provisional table of the families and genera constituting the 

 Leptonacea 1 is adopted. Montacuta bidentata Montg., and Kellia 

 planidata Stimp., are both placed in the genus Rochefortia Velain. 

 Lascea rubra (Montg.) is thoroughly discussed. Dr. Dall finds no 

 permanent specific character to separate L. bermudensis Bush. 

 " Small shells like Lascea which attach themselves by a byssus to 

 alga?, may be widely distributed by ocean currents. Differences of 

 temperature and food cannot fail to make their mark upon the differ- 

 ent colonies. When, in addition, we have a normal crudity and 

 want of definition in the hinge characters throughout the genus, it 

 would seem inadvisable to subdivide the type too minutely." 

 Montacuta elevata Stimp, is placed in the genus Aligena H. C. Lea. 



The work closes with the Diplodontuhe ; a synopsis of the recent 



1 A synopsis of the Recent and Tertiary Leptonaccea of North America and 

 the West Indies, was published by Dr. Dall in the Proc. U. S. Nat. Mus., xxi, 

 pp. 873-897, 1899. 



