58 



of Pennant. The Jlria. notch the margin very finely, and 

 fome few fligl)t flria run acrofs tlie lliell." Donovan has 

 given an exceedingly good figure of a Peclen \\v<xi e\?i6\.\y 

 accords with Da Costa's defcription, and quotes that author's 

 parvus as well as Pennant's obfoletus, but neitlier of diefe 

 writers remark the uioft , eflential cliara6ler, , the minutely 

 fine decuflat€ Jliiie, that appegx junker a powerful lens like 

 fliagreen ; for in other refpe61:s fcarcely two fpecimens are 

 to be found alike. It is not furprifing that Mr. Pennant 

 fhould call his fliell fmoofh, oi* that any other conchologifi:, 

 not in the habit of examining attentively by glafles, fliould 

 have overlooked that circumftance, for it is not apparent to 

 , the naked eye ; indeed we acknowledge ourfelves to have 

 been deceived in the firft fpecimen we obtained, which hajv 

 pened to be a variety without any ribs, and that a]>pcared to 

 the naked eye.perfedllyfmooth. This we had placed in our 

 cabinet as the PeSlen Icevis of the BritiJJj Zoology ; and other 

 varieties occurred, which we defcribed as that Ihell^ not hav- 

 ing been able at that time .to compare the three fpecies in 

 queftion. Since that peri<:)d we have fortunately obtained 

 each, and amowgft the obfoletus fo many varieties that it is 

 fcarcely poflible to identify it by the defcriptions hitherto 

 given, or to fix any charafter but the invariable fliagreen 

 appearance. Some, it is true, poITefs the eight or ten ribs 

 more prominent tlian the reflj while a greater number are 

 quite plain, or defiitute of ribs ; others have more numerous 

 intermediate ribs near the margin. A fpecimen before us 

 has fifteen faint ribs without any larger. Another variety 

 from Mr. Laskey (who found it mStcftand,) has thirty fine 



obfolete 



