54 Journal op conchology, vol. 9, no. 2, april, 1898. 



Before proceeding further it was necessary for me to establish the 

 identity of my Plymouth specimens with Mr. Marshall's "new shell," 

 for there was a possibility that the shell had been correctly described, 

 and that the artist had so misrepresented it as to give it a wholly 

 different dentition, and one which by chance agreed entirely with that 

 of my shells. I mounted two valves, sent them to Mr. Marshall for 

 examination and received the following answer : — " I can only speak 

 of one of your Plymouth valves, which is similar to Scintilla eddystonia 

 in size and every other respect ; the smaller valve I have not ventured 

 to touch. The dentition of the Plymouth shell is similar but not 

 identical with that of Diplodonta." Now, I have carefully re-examined 

 these shells, and have compared them with a full series of Mediter- 

 ranean Diplodonta, ranging from less than -^ of an inch across to the 

 full size. I have submitted both to a number of competent and well- 

 known conchologists not one of whom finds any difference. The 

 hinge structure is that of Diplodonta as given in Woodward's ' Manual.' 

 Quite recently a number of minute Diplodonta from Bantry Bay have 

 further confirmed the correctness of my opinion. There is never any 

 trace of a lateral tooth or anything that could be easily mistaken for 

 one. There is a ledge bounding the groove for the insertion of the 

 remarkably placed ligament, but that could scarcely be mistaken 

 for a tooth. I must therefore conclude that I was right in supposing 

 that Mr. Marshall mistook the uncleft cardinal for a lateral. 



Mr. Marshall seems also to have misconceived the figure accom- 

 panying Jeffreys' description of Diodonta barleei which he states 

 "could not be better." There are on the same plate obvious errors 

 of drawing, and in the present instance the figure does not agree with 

 Jeffreys 5 description and especially with his statement that the shell 

 bears some resemblance in form and size to Montacnta substridta. 

 Who would dream of likening this species to the figure with its wholly 

 different form and nearly central umbo? The comparison is quite 

 applicable, however, to the actual shells. 



In a foot note to his paper on the Marine Shells of Scilly in this 

 Journal for October, 1897 (vol. 8, p. 433), Mr. Marshall has 

 again erred in the way of careless misquotation. I did not say that 

 the earlier stations of the 1870 'Porcupine' Expedition were in the 

 S. and S.W. of Ireland. I should almost as soon have thought of 

 saying that Iceland was in the N.W. of Scotland. All these stations 

 however lie between the meridians of Valentia and Galley Head at a 

 distance of some 180 — 190 miles from land, and I venture to think 

 that my description of their position was far better than Mr. Marshall's 

 vague talk about the entrance to the British Channel. 



