226 

 Area continued. 



mytiloides. . oblong, very smooth, obsoletely striated longitu- 

 dinally ; valves compressed in the middle. . Plaisance. 



Pectunculus. 



pulvinatus. . orbiculated, transverse, subequilateral ; with longi- 

 tudinal grooves and striae ; beaks small. . Grignon. 

 Analogue of P. glycemeris ? 



cor. . obliquely cordate ; tumid ; with longitudinal, rather 

 distinct grooves ; base subturgid. . Bourdeaux. 



obovatus. . convex, subequilateral ; very thick, superior margin 

 rounded ; no longitudinal strise. . Weissenstein. 



planicostalis. . ovato-orbiculate ; ribs numerous, small, flat, 

 angular on one side ; transverse strise obsolete. . Pont- 

 chartrain. 



transversus. . elliptical transversely, rather tumid ; equilateral ; 

 remote longitudinal grooves, with very fine decussating 

 striae. 



nudicardo. . transversely elliptical, tumid ; hinge, without teeth 

 in the middle ; but few at the extremities. 



subconcentricus . . suboval, rounded, convex, longitudinally 

 striated ; some distant, transverse, concentric grooves on 

 the upper part. 

 An. P. decussatus, Sowerby ? 



nummiformis. . lenticular, not eared, rather smooth ; transversely 

 concentric, and longitudinal strise, blended or separate. . 

 Touraine. 



pygmceus. . orbicular, subequilateral, depressedly convex, small, 

 with transverse and decussating longitudinal striae. . 

 Grignon, 



nuculatus. . inequilateral, obliquely transverse ; very fine trans- 

 verse striae ; beaks conniving. . Grignon. 



Nucula. 



rostralis. . transverse, oblong, gradually rostrated forwards, 

 base tumid ; corselet concave, lanceolated. . Bourgogne. 



emarginata. . ovate ; striae obliquely transverse; foreside pro- 

 duced. 



deltoidea. . triangular, inflated ; foreside obliquely truncated ; 

 rounded backward ; corselet flat. . Grignon. 



placentina. . ovately transverse ; rather large, oblique, longitu- 

 dinally striated, pearly within, margin crenulated. 



margaritacea. . obliquely ovate, subtriangular, rather smooth, 

 internally pearly ; prominent hinge tooth. . Grignon. 



striata. . ovate, subplicated forwards, with elegant transverse 

 strise ; no hinge tooth. . Grignon. 



Trigonia. 



scabra. . ovato-trigonal, produced forwards, with transverse 



tuberculatedly scabrous ribs. 

 T. spinosa ?. . St. Paul-Trois chateaux. 



