THE NAUTILUS. 135 



Remarks. This species belongs to the group of which U. trigonus 

 Lea, may be considered the type, although differing much from that 

 species in outline, beaks and in the uniform roundness of the sides. 

 It also has certain characters indicating a relationship with U. 

 Ride/Hi Lea, U. Chunii Lea and U. cuneus Con. It differs from the 

 first in having the posterior apex lower and more or less biangul- 

 ated ; the posterior margin rounded, instead of straight; posterior 

 margin without the hip peculiar to T. Ri<lellii; the cardinal teeth 

 are heavier and not pyramidal ; and differs most remarkably in the 

 character of the beak undulations. From U. Chunii Lea, it differs 

 in having a greater depth of cavity ; more massive and higher urn- 

 bones and swollen sides without depressions ; much shorter poste- 

 rior extension; base not emarginate; entire absence of rays and 

 the same difference in beak undulations that distinguishes it from 

 U. Ridellii Lea. It differs from U. cuneus Con. in being smoother ; 

 lighter colored epidermis ; much larger opening to the umbonial 

 cavity ; cavity of the shell much deeper and more uniformly rounded ; 

 lateral teeth more slender and the species never attains the extreme 

 size of U. cuneus, the declivity of the posterior slope is much steeper ; 

 the ligament shorter ; without the anterior subtruncation, and it is 

 never cuneiform. 



The peculiar undulations of the beaks amply distinguish it from 

 any other known species. 



Some twenty-five specimens have been critically examined which 

 maintain a remarkable constancy in all the characters. 



It is named in honor of Mr. Lorraine S. Frierson of Frierson 

 , La. who is a zealous student and collector of Unionidse. 



ON CERTAIN ABNORMAL SPHJERIA. 



BY BRYANT WALKER, DETROIT, MICH. 



The peculiar characteristics of the hinge-teeth of the American 

 species of Sphserium and Pisidium have been almost totally ignored 

 by Prime and the earlier writers in their descriptions of the various 

 species which they established. With the exception of some of the 

 descriptions of the more recently described species, nothing but the 

 most general remarks upon the subject are to be found in the Amer- 

 ican literature upon these genera. Among the European concholog- 



