THE NAUTILUS. 



11 



species of this genus are usually very abundant in their chosen 

 places. 



Recently Mr. G. Willett, warden of the Forrester Island res- 

 ervation in southern Alaska, has succeeded in getting an excel- 

 lent shell-collection at this isolated spot; among the shells thus 

 obtained was a good series of Astarte compacta. With this, and 

 for a time confused with the latter, is what seems to be a new 

 species of Astarte, which Mr. Willett in arranging his collection 

 was the first to discriminate. He had the kindness to send me 

 his fine mounted series of both species for examination, the re- 

 sult of which is not only that a new species is identified, but 

 it is shown that A. compacta as well as the new form belong to 

 the typical section of the genus, both forming at intervals cren- 

 ulation of the inner margin of the valves. The only specimens 

 of A. compacta previously available happened to be in the stage 

 without crenulations. 



The new form is best described by a comparative diagnosis. 



Astarte willetti, n. Bp. 



Shell small, of a yellowish-brown externally, milk-white in- 

 ternally ; the external sculpture of small concentric waves is 

 more regular and constant than in compacta ; the form is more 

 oval and the beaks more anterior than in that species, and wil- 

 letti appears to attain a larger size. In compacta the lunule is 

 relatively narrower and longer than in the new species. In the 

 interior the hinge of the latter is better developed than in com- 

 pacta, all three teeth being usually represented, while in com- 

 pacta the posterior and particularly the anterior cardinal is fre- 

 quently obsolete or absent. The shell substance of A. compacta 

 is more translucent and bluish, and the crenulations of the valve 

 margin when present are distinctly smaller and less conspicu- 

 ous than in willetti. 



The measurements of two forms are as follows, the largest 

 specimen of a series of some twenty-five specimens being selected 

 in each case. 



Height. Length. Diameter. 



A. willetti 14 16 8 mm. 



A. compacta 12 12 6 mm. 



