MARYLAND GEOLOGICAL SURVEY 725 



Pholas pectorosa Conrad, 1854, Jour. Acad. Nat. Sci., Phila., 2d ser., vol. ii, 



p. 299, pi. xxvii, fig. 9. 

 ? f Pholas cithara Meek, 1864, Check List Inv. Fossils, N. A., Cret. and 



Jur., p. 16. 



f ? Clavipholas cithara Conrad, 1868, Cook's Geol. of New Jersey, p. 728. 

 ? f Martesia cithara Gabb, 1876, Proc. Acad. Nat. Sci., Phila., p. 304. 

 Pholas cithara Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 187, pi. 



xxv, figs. 14-16. (Synonymy excluded.) 



Pholas pectorosa Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 18. 

 Pholas cithara Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p. 



651, pi. Ixxiv, fig. 7 (ex parte). 



Description. " Ovate-cuneate ; anteriorly inflated, contracted in the 

 middle ; posterior side cuneiform ; disk with radiating ribs, largest ante- 

 riorly, and interrupted by concentric furrows; anterior side very short, 

 margin obtusely rounded or subtruncated ; basal margin rounded ante- 

 riorly, contracted medially, straight posteriorly." Conrad, 1854. 



Type Locality. Tinton Falls, Monmouth County, New Jersey. 



" Shell triangularly ovate, acutely pointed behind and subtruncate in 

 front. Valves very ventricose, the depth and thickness when united 

 about equal, giving a nearly round section. Anterior umbonal ridge 

 inflated and nearly subangular in some cases, always sharply rounded, and 

 the anterior surface somewhat flattened or but little convex. Central 

 region of the valves sulcated obliquely, more or less constricting the front 

 margin at about or just behind the center. Hinge line straight, deeply 

 sunken betwen the large, inflated and enrolled approximate beaks. Surface 

 of the shell marked by strong radiating ribs, numerous but somewhat 

 irregular posterior to the umbonal angle, but few and distant in front; 

 also by comparatively strong concentric ridges, which are distinctly 

 deflected at the mesial sulcus and pass obliquely upward in front of it. 

 These concentric ridges form flattened nodes of the radiating ribs by 

 crossing them on the anterior part of the shell. 



" I have seen several casts of this species, and noticed considerable 

 variation in their characters, especially in the strength of the surface 

 markings, in the form of the anterior end, and in the strength of the mesial 

 sulcus of the valves, and especially in the strength and character of a 

 sometimes deeply impressed but narrow line marking the bottom of the 

 sulcus and dividing the anterior and posterior sections of the shell, it 



