THE NAUTILUS. 



21 



natecl from a coiled form, and is not as supposed by some pakeon- 

 tologists the original form of the Ammonitidce, but is rather to be 

 looked upon as an uncoiled form developed from originally coiled 

 parents. 



ON THE GENUS TEBENNOPHORUS BINNEY, OR PHILOMYCUS, RAF. 



(CONTINTED.) 



BY H. A. PILSBKY. 



Article III. (Ann. Mag. N. H., March, 1891.) 



Letter from Mr. T. D. A. Cockerell to Eds. Ann. Mag. N. H. 



The Genus Limacella. 



On pp. 184-186 of the February number Mr. Pilsbry has some remarks on the 



genus Tebennophorus or Limacella, to which I may perhaps be j ermitted to reply, 



taking his several points in order. 



(1) That plate of Blainville's has certainly received bad treatment. The figures 



have been inaccurately copied ; Ferussac quoted it wrongly ; and now, as 

 Mr. Pilsbry has shown, I also have erred with regard to it ! There are two 

 figures iv., labelled respectively 1 and 2. Fig. 2 is obviously Veronicella, 

 but fig. 1, for which alone my reference was intended, looks like Limacella, 

 though from Blainville's text it is clearly intended for Veronicella also. I 

 quite agree with Mr. Pilsbry that fig. iv. no. 1 might or might not from its 

 appearance be of the genus under discussion ; and as it is stated to be Ver- 

 onicella, there apparently remains no doubt that my reference of it to Lim- 

 acella was erroneous. I am still of the opinion, however, that fig. v. rep- 

 resents the genus Americans writers call Tebennophorus. 



(2) There is, I think, no doubt about the slugs I described being Blainville's 



types ; nor are these the only British-Museum slugs described by Blain- 

 ville. The Museum is mentioned in the original paper. 



(3) It is very difficult to say whether inaccuracy of description, when there is no 



doubt what was intended, ought to condemn a name. If so, there will have 

 to be considerable slaughter of the genera described by early authors, or, 

 for that matter, by some recent ones. Philomycus, which Mr. Pilsbry 

 thinks might be adopted, was also inaccurately defined. So far as is known 

 there is no slug in existence really agreeing with the original descriptions 

 of Limacella or Philomycus taken literally. 



(4) Limacella, Brard, if it is anything, is Limax of modern authors, not Agrio- 



limax. But a genus founded for the shells only of species of the Linnean 

 Limax cannot be recognized as valid, and the only authors who have 

 adopted it are Dr. Jousseaume (1876) and Dr. Turton. The former 

 writes Limacella for Limax auctt., and Limax for Arion ; while Dr. Tur- 



