FoJJil Anomia- found h Derby/hire. 49 



beak of the larger valve. It is not however con flan tly placed in 

 that fituation, as one of the recent fubjects, the Anomia Ephippium, 

 Lin. Syjl. p. 1150, and the foflil defcribed in the preceding pages, 

 evince. Nor does it appear that it fhould be coniidered as a prin- 

 cipal or determinate charatteriftic of this family ; for in examining 

 fome hundred fpecimens, fimilar to thofe reprefented by fig. 7, 8, io, 

 as well as all the different fpecies which come under the divifions 

 thofe figures elucidate, I have not been able to detect the fmalleft 

 aperture in either of the valves, though many of the- fpecimens 

 were far more perfect than fome of thofe in which the perforation 

 is always fufflciently vifible. I am well aware that fome of thefe 

 imperforate Anomia: would be ranked by Conchologifts, who efteem 

 the aperture as the leading character, under another genus ; for in- 

 flance, the Anomia Gryphus, and other fpecies of a like form, with 

 the Oftrea, But though there may be fome doubt refpecting the 

 family to which the foffils in queftion properly belong, certainly 

 there is no genus yet eftabliihed, except Anomia, that will receive 

 thofe imperforate bivalves reprefented by fig. 7, 8, 10. Muft we 

 therefore form a new genus for the fubjects under confideration, or 

 adhere to the definition of an Anomia Linnceus has left us, in which 

 the. perforation is not, I think, confidered as a conftant generic 

 character ? Perhaps till more accurate in ve negations prove the hinge 

 (from which without doubt the leading character in every family of 

 bivalves fhould be taken) in the perforated Anomia-^ to differ from 

 that of the imperforate, it will be advifable for thofe who are en- 

 gaged in the purfuit of extraneous fofftls to confider all bivalves with 

 unequal valves, the beak of one being produced or more prominent than that 

 of the other (generally the /mailer valve), and for the mojl part m curved 

 over the hinge, as belonging to the genus of Anomia* 



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Vol. IV. U An 



BOTANICAL* 

 GARDEN. 



