C. semiorbiculata. Sp. semiorbiculatus compressus, decussate striatus, rudis.
"Interior" was the earlier reading of "primarius."
C. cordata. Sp. cordatus, transversim striatus, hinc elongatus, compressus.
C. oblonga. Sp. oblongus, antice angulatus, dentibus anticis acutis.
"Unico" (error for "unicus") originally preceded "in altera valvula."
C. cordiformis. Buc. subrotundum læve, umbonibus recurvatis.
The brief description in the 'Systema' had evidently been copied in the manuscript by our author himself, who cited Gualt. t. 71. f. E. as the sole synonym. The specimen had apparently been added to the collection, subsequently to the drawing up of the first catalogue.
ARCA.
Testa crassa, umbonibus distantibus intus fornicatis. Cardo planus, masticatus dentibus numerosis minimis æqualibus transversis.
A. tortuosa. A. oblonga obliqua, valvula altera oblique carinata.