191 



F. acuticosta differs from the preceding chiefly in having its ribs some- 

 what carinated ; Lamarck, indeed, suspects it to be merely a variety. 



V. senilis. Lam. is a thick obliquely cordated shell, about an inch and 

 a half in length, with large convex, rather imbricated, but not rough, 

 ribs. The specimen possessed by Lamarck, he believes, was obtained 

 from Courtagrion. It is frequently found among the Harwich shells, and 

 in very good preservation. Its thick valves, with large smooth ribs, give 

 to it a very antiquated appearance. The outer and inner side of one of 

 these shells are figured Plate XIII. Fig. 15 and 17. Lamarck particu- 

 larizes two more species, V. multicostata, V. pectuncularis ; besides four 

 more, V. cor avium, V. squamosa, V. decussata, and V. elegans ; in which 

 only one hinge-tooth is apparent in one valve, and which is received by 

 two corresponding but diverging teeth in the opposite valve. 



CXIX. Lucina. A round, or ovato-transverse equivalved bivalve, 

 with the beaks bowed backwards. The hinge teeth, one or two, varia- 

 ble ; the lateral teeth one or two, and sometimes hardly any. 



These shells differ from Venus's, in having lateral teeth ; from Tellens, 

 in having no fold ; and from Cyclades, in not having three hinge-teeth. 

 Lamarck reckons twelve species as found in the neighbourhood of Paris: 

 L. lamellosa, L. concmirica, L. circinaria, L. sa.wrum, L. divaricata, L. gib" 

 bosula, L. rcnulata, L. albella, L. sulcata, L. squamosa, L. undulata, L. com- 

 planata. 



This genus was instuted by Bruguiere for the reception of those shells 

 which, with only one or two cardinal, had one or two lateral remote 

 teeth, which in some species were hardly apparent. Tellina pectinata, 

 Linn. Conchy L Listen, PL 300, Fig. 137, is one of this genus: V.fim- 

 briata, Linn. V. Pensylvanica, Linn, with T. lactea, Linn, and T. diva- 

 ricala, have been also placed in this genus. 



A small shell, resembling V. gallina, found among the Harwich fossils, 

 seems to have the characters of this genus. 



CXX. Tellina. An orbicular or ovate-transverse, equivalved bivalve, 



