48 PROCEEDINGS OF THE ACADEMY OF [Feb., 



end evenly rounded from umbone to base. Posterior end some- 

 what obliquely produced and obscurely truncate dorsally, rounded 

 laterally. Base very gently curved. Umbones inconspicuous, 

 opisthogyrate, placed a little in front of the median line. Lunule 

 rather narrow, clearly delimited. Escutcheon narrow, somewhat 

 elongated. 



Sculpture. — External sculpture typical of the genus in general 

 character. Posterior portion of the valve slightly depressed but 

 not angulated, sharply differentiated, however, by the discrepant 

 ornamentation. Medial and anterior positions covered with fine, 

 chiselled grooves which extend from the boundary line of the 

 posterior area and from the ventral margin obliquely upward 

 and forward to the umbones and anterior margin. Grooves of 

 posterior area arranged in crowded concentric chevrons with a 

 high apical angle directed toward the umbones. 



Ligaineni.— internal characters as in Strigilla flexuosa Say. 

 Ligament external, opisthodetic. 



Dentition. — Right valve armed with a very small, simple, an- 

 terior cardinal, a much more prominent bifid posterior cardinal, 

 and a strong, posterior and anterior lateral. Dentition of left 

 valve reduced to a moderately stout anterior, and a very slender, 

 laminar, posterior cardinal. Dorsal margins slightly modified to 

 function as laterals. 



Muscle Impressions and Pallial Line. — Muscle impressions indis- 

 tinct. Anterior somewhat more elongated than the posterior. 

 Pallial line rarely discernible, its dorsal margin a low arch extend- 

 ing from the ventral boundary of one adductor to the ventral 

 boundary of the other, rising a little higher in the left valve than 

 in the right, but not even in its maximum elevation overreaching 

 the medial line of the adductors. 



Dimensions.- — Altitude of type, 10.7 mm. Latitude, 11.0 mm. 

 Semi-diameter, 3.3 mm. Altitude of other figured individuals, 

 10.1 mm.; 8.7 mm. Latitude, 10.5 mm.; 9.3 mm. Semi-diameter, 

 2.8 mm.; 2.2 mm. 



Type Locality. — Walker's Bluff, Cape Fear River, Bladen County, 

 North Carolina. Waccamaw Formation. 



Observations. — Representatives of this species have formerly been 

 included under Strigilla flexuosa Say. Say's type is not avail- 

 able at present nor does he give a specific locality. From a com- 

 parison of his description and the recent material in the reference 

 collections in the National Museum, it seems probable that the 



