Genus Puncturella. 77 



amined, the anterior lateral valves are furnished with the shoulder, 

 one on each ; while the anterior valve itself is unprovided and 

 simple. In other words, in B. punctutus^ both the anterior and 

 posterior valves are furnished each with two connecting shoulders; 

 in all the other British species, the posterior valve onlij is fur- 

 nished with two; the lateral valves with one each; and the an- 

 terior valve is without any. 



This character has been proved constant by the examination 

 and dissection of a great number of specimens, from very different 

 localities. The punctured appearance, and the locking together of 

 the valves of the operculum, have been found very inconstant ; but 

 the character here mentioned is invariable ; and from its sim- 

 plicity and obviousness, entitles its discoverer to the highest 

 praise. 



Patella apertura of Montagu has been ascertained beyond a 

 doubt, by my friends Mr. Clark and Mr. M. J. Berkeley, to be 

 nothing more than the young of Fissurella grceca. As the shell 

 advances in growth, the spiral vertex becomes gradually more 

 eroded, and finally quite disappears. Some specimens of this 

 shell in the young state, have been named by Dr. Leach in the 

 British Museum, Cemoria MontaguL They are there placed as 

 a second species, with another shell communicated by Dr. Flem- 

 ing, which is named Cemoria Flemingii. This last, though a very 

 imperfect specimen, I have little doubt is identical with a shell 

 found by myself in 1824, at Oban in Argyllshire; and which 

 appears not to differ in any respect from Patella fioac/iina of 

 Linnsus, and Chemn. 1. 197. f. 1927, 1928; and Patella fissurella 

 of Mull. Zool. Dan. t. 24. f. 4—6. 



Since the name Cemoria has not, as far as I am aware, been yet 

 published as attached to this shell, which appears to me the type 

 of a distinct group of the Calyptraciana, I propose to substitute 

 for it the name of Puncturella^ which is somewhat more expres- 

 sive of the peculiar character. In our present ignorance of the 

 animal, this is meant to be proposed as a distinct genus merely 

 provisionally/. All my specimens, unfortunately, were found with- 

 out the animal. 



