THE NAUTILUS. 21 



Pis. vesicnlare n. sp. 



Mussel small, ovoid, very inequipartite, somewhat oblique, strongly 

 inflated ; beaks very posterior, moderately prominent ; margins all 

 well rounded, or the scutum forming a very slight angular projec- 

 tion ; color yellowish to brownish-horn ; surface slightly striated, 

 polished, often with a few coarser lines of growth ; shell thiu, trans- 

 lucent ; nacre rather glassy, colorless ; hinge rather small, markedly 

 short; cardinal teeth lamellar, the right moderately curved with its 

 anterior end thicker ; anterior left distinctly directed upward, curved, 

 often angular, posterior oblique, moderately curved ; groove between 

 them narrow and deep ; lateral teeth situated very close to the car- 

 dinals, short, especially those in the left valve abrupt, high ; liga- 

 ment short. 



Size: long 2'3, alt. 1'9, diam. 1-7 mill. 



Habitat. Michigan. 



More than fifteen hundred specimens were seen during the last 

 year, collected at Grand Rapids, Michigan, by Mr. L. H. Streng 

 about ten years ago, and all were remarkably uniform in shape and 

 appearance. Yet I hesitated to announce the form as a uew species, 

 thinking it might be a variety of P. ventricosum Prime. But later 

 it has been seen from various other places, as Lake Michigan, Hess 

 Lake, " Michigan," in one instance named " P. rotuiidatuin," from 

 which it is very different by its beaks situated posteriorly, while in 

 rotundatum they are almost in the middle. 



P. cesiculare can be mistaken only for P. ventricosum Pr., from 

 which it differs by the following characters : it is longer, less oblique- 

 more regular in form, being more regularly though less inflated, the 

 beaks are much less prominent; the surface shows less coarse and 

 irregular lines of growth. It is somewhat variable in size, measur- 

 ing 2'l-2'7 millimetres in length, and in being slightly more or less 

 inflated. 



A NEW VARIETY OF PUNCTUM. 



BY H. A. PILSBRY. 



Punctual conspectum var. pasadenae n. var. 



Shell resembling P. conspectum Bid., but more widely and openly 

 nmbilicated, and without spaced riblets, or with them very 



A>C3^ 



te LURARY 



a openly 



