444' Prof. E. Forbes's IleplT/ to Prof. A. Leymerie 



impression is that M. d'Orbigny is right, and that the 

 British and French forms are varieties of one species ; and if 

 so, they certainly should be referred to C. exaltata, rather 

 than burden our lists with a new name. 



5th. " Pinna sulcijh-a." — The identification of Pinna sulci' 

 fera with Pinna tetragona of the Mineral Conchology is, no 

 doubt, wrong. I was led to do so in consequence of M. 

 d'Orbigny having identified a British example of the latter, 

 forwarded through Mr. Pratt, with the French species above 

 mentioned. Subsequently specimens of the English shell, 

 laid before the same naturalist by Dr. Fitton, were named by 

 him Pinna Robinaldina, a Neocomian species, which he has 

 since described and figured; so that if Pinna sulcifera be 

 not English (though I have reason to believe it has been found 

 here also), our common lower greensand Pinna still turns out 

 identical with a French Neocomian species. The name tetra- 

 gona of Sowerby must be dropped, as it was adopted by that 

 author from a mistaken reference of the shell to a species de- 

 scribed by Brocchi; as also must the new name Robinaldina, 

 and that of restHuta, under which it had previously been de- 

 scribed by Hoeninghaus and figured by Goldfuss, adopted in- 

 stead. 



6th. " Pecten inter striatus" — Specimens of Pecten obliquus, 

 identified by comparison with the original types, were for- 

 warded to France and returned as Pecten interstriatus ; and 

 French specimens, brought to England by Dr. Fitton, exactly 

 agreed with our own. The figure of Sowerby is no doubt 

 bad, not from faulty drawing, but in consequence of having 

 been taken from the first specimen found, and that a bad one. 

 But when M. Leymerie denies our identification of species 

 with Sowerby's types, he should recollect that those types are 

 on this side of the Channel, and a great number of them still 

 accessible. The probability is certainly in favour of our know- 

 ing our own species best. 



7th. " Modiola Archiaci." — This I identified with Modiola 

 aqualis, and M. Leymerie seems inclined to admit the iden- 

 tification. I am now convinced, from the examination of 

 French specimens, that they are certainly identical. The spe- 

 cies is a variable one, and varieties resembling the figures of 

 M. Leymerie and of Sowerby are equally common, passing into 

 each other by insensible gradations. [ do not understand 

 why M. d'Orbigny has lately separated his M. Archiaci, not 

 only specifically, but generically from M. ceqnalis, calling it 

 Lithodomus Archiaci, unless it be that it is sometimes a perfo- 

 rating species. That, however, is the case with some recent 

 Modioli, which are sometimes free and sometimes perforators. 



