ERRATA ET CORRIGENDA. 
Page 10, line 6, dele modice. 
“17, “© 97, for 58, read 59 
“ 99 * 9g], & 27, «“ 28. 
“ 23, “ 20, “ Ostesdesma, “ Osteodesma. 
PEcTEN Fuscus, Linsley. This name is preoccupied by Klein. It must 
therefore receive a new one. I would propose that of P. brunneus. 
LEpDA OBESA, St. As will be seen by the figure, this species is remark- 
able for the reduction of the prominent support for the internal liga- 
ment. 
The abbreviation f occurring in this work signifies fathoms. The 
depths are all reduced to low-water level. 
CAMBRIDGE, Nov. 25, 1851. 
