70 . R. BULLEN NEWTON on 



furnished with about fifty minute slightly divergent denticles, terminal largest 

 and most oblique, obsolete beneath the umbo, rather fewer anteriorly than 

 posteriorly ; inner margin smooth. 



DIMENSIONS. 



Small form. Adult form. 



Height 4 ... 10 millimetres. 



Length 8 ... 20 



Diameter (united valves) ... 4 ... 8 



REMARKS. The chief features of this shell concern its more or less 

 cylindrical contour, the nearly central umbones, and the occupation by the 

 striated ligament lozenge of the entire ligament furrow, the latter character 

 having been referred to by Dr. Dall l as typifying Conrad's Striarca of the 

 United States Miocene, under which this new species is here recognised ; 

 being therefore distinguishable from Fossularca, which ranges from Eocene to 

 recent times, that shell having a shorter ligament lozenge with a bare space at 

 both ends of the ligament cavity. This form apparently exhibits little 

 relationship to any of the Arciform species from the European Tertiaries 

 which, generally speaking, possess much more inaequilateral valves, besides 

 being relatively wider. The species is quite well represented, although the 

 examples are not numerous. The valves are observed to be frequently 

 perforated at the umbonal arch, suggestive of an attack by a Serpula or 

 other organism in an attempt to reach the soft parts of the mollusc for purposes 

 of food. 



OCCURRENCE. Cuttings Nos. i, 5, 6, 10, 12, 14. 

 COLLECTOR. Mr. Kitson. 



Anadara nigeriensis, sp. nov. 

 PLATE 8, figs. 4-7. 



DESCRIPTION. Shell subquadrate, posteriorly oblique, convex, equivalve, 

 inaequilateral, length about one-tenth in excess of the altitude ; anterior 

 margin rounded, posterior region obtusely carinated, abruptly deep, oblique, 

 ventral border slightly curved ; ligament furrow narrowly lanceolate, chiefly 

 anterior, shorter, broader and more saggitate posteriorly, perpendicularly 

 striated, not chevroned ; umbones anterior, incurved, moderately distant ; 



1 Trans. Wagner Free Inst. Sci. Philadelphia, 1898, Vol. 3, part 4, p. 615. 



