288 PROCEEDINGS OF THE ACADEMY OF [Sept., 



strongly shouldered and unicarinate; protoconch scar small; body 

 broad and angular, the peripheral area narrow, flattened, biearmate, 

 the posterior body slope broad and conspicuous, the anterior slope 

 is a little more gentle and a little broader than the posterior slope, 

 especially in old individuals; sculpture both axial and spiral, spiral 

 ornamentation consisting of the two carinse on the periphery and six 

 or seven low spiral ridges on the anterior slope of the body and on the 

 pillar; posterior slope of whorls free from well defined sculpture; 

 spirals intersected by deeply angular and laminar axials which are 

 irregularly spaced and about twenty or less in number on the body; 

 spirals spinose at the intersections of the incrementals; spines strong- 

 est along the posterior carina, anterior carina an aggregation of six 

 or seven strong spiral threads that terminate sharply at the incre- 

 mental lines, making axials at these points finely serrate; three or 

 four similar threads appear between the two carinse on the peripheral 

 area; on the anterior slope of the whorl spines are low or tuberculate; 

 aperture ovate, slightly angular behind and produced in front into 

 a long, narrow canal with proximate parallel margins; margin of 

 outer lip thin, deeply angulated at the posterior carina, abruptly 

 constricted at the base of the body; inner lip excavated medially, 

 reflected and adnate on the body and the pillar on immature indi- 

 viduals ]3ut not in adults, a deep, broad and elongate cavity developed 

 in mature forms between the inner lip and the pillar; columella 

 smooth ; pillar slender, slightly curved or bent in an irregular manner 

 near the anterior extremity. 



Dimensions (slightly imperfect individual). — Altitude 26.6 mm.; 

 maximum diameter 25.2 mm. 



This species is well characterized by its pyriform outline, and 

 especially by its bicarinate widely expanded body which is ornamented 

 with laminar spinose axial lines. It is common at Coon Creek and 

 represented in the present collection by a number of individuals 

 which show a wide variation in form and size. Further collecting 

 at the type locality may result in the isolation of other species of 

 this group. An undescribed tricarinate species of this genus occurs 

 at Owl Creek, Mississippi. 



Genus LIROSOMA Conrad. 

 Lirosoma cretacea n. isp. PL XVIII, figs, o, 6. 



Description. — Shell fairly large and stout, pyriform; spire low and 

 obtuse, its elevation less than half the total altitude of the shell; 

 whorls five to eight in number, strongly and evenh'^ convex, rapidly 



