5i Olsson, Neocene Fossils 13 



Modiolus gigantoides, n. sp., . Plate 2, Fig's 1-3 



Shell large, heavy, convex, elongated ; beaks placed rather 

 near the anterior end of the shell ; anterior end narrow ; shell 

 highest just about the middle ; posterior end acutely rounded ; 

 dorsal margin straight and deflected at an angle of about 30 ; an- 

 terior portion with two well-marked depressions extending from 

 the beak to the basal margin, and with a prominent ridge be- 

 tween ; surface marked with coarse lines of growth with little or 

 no signs of resting stages ; anterior end slightly projecting be- 

 yond the beaks, with thickened lamellar margin. 

 Length 98, height 50, thickness jp mm. 



This species is characterized by its large size, convexity, 

 heavy shell and the lack of the prominent, impressed, dorsal area 

 of M. ducatelli Con. From M. gigas Wagner to which it is al- 

 lied most closely, a marked difference is found in its much less 

 expanded posterior end, greater convexity and less pouting anter- 

 ior end. M. gigas has for some time been considered as doubt- 

 ful because of its rarity and abnormal appearance. Last sum- 

 mer, however, a single, more or less imperfect specimen of a Mod- 

 iolus was collected at Yorktown which agrees in all essential char- 

 acters with the figure of M. gigas except in the matter of size, the 

 specimen measuring 65 mm. in length. This shell possesses the 

 wide, expanded posterior end but lacks the less pouting anterior 

 end. 



Miocene{f); Lake Waccamaw, N. C. 



Lithophaga yorkensis, n. sp., Plate 2, Fig's 5, 6, 10 



Shell small, thin, in shape more or less like Lithophaga aris- 

 tata Dillwyn but differs in being constantly shorter and in lack- 

 ing entirely the twisted process which projects from the posterior 

 end of that species ; surface smooth, with only very fine growth 

 lines and occasionally incised lines, representing resting stages ; 

 a ray extending from the posterior end of the shell to the 

 beak along which the resting marks are well developed ; five 

 or six discontinuous faint raised lines extend from beak toward 

 basal margin in a posterior direction ; shell loosely surrounded 



