376 On the Mollusca of Europe and North America. 



consulted the recent edition of Gould's ' Invertebrata of Massa- 

 chusetts,' and found it a most useful guide. If Prof. Verrill is 

 dissatisfied with that work, he may directly criticise it to his 

 heart's content ; but he ought not to indirectly criticise it 

 through me. 



As to the difference of certain species (9 only out of 401 

 species) I would observe as follows : — 



1. Gemma gemma. I am by no means sure that this is not 

 the fry of Venus mercenaria, although Prof. Verrill has far 

 greater opportunities than I have for deciding the matter. 



2. Area transversa. This may be distinct from A. pexata, 

 and not merely a variety of it ; but Prof. Verrill is evidently 

 fond of adopting genera founded on unimportant characters, 

 and his proneness to multiply species also may therefore be 

 assumed as probable. 



3. Mactra avails. I cede the point to Prof. Verrill as to this 

 being distinct from M. solidissima. I had not seen specimens 

 of M. ovalis and the preceding two controverted species, and 

 only formed my opinion from Gould's work. 



4. Astarte castanea. A. horealis and other species of the 

 same genus are so polymorphous that I was justified in saying 

 A. castanea is " perhaps a variety of A. horealis. ^^ I fully 

 expect to see a connecting link between them. The same 

 observation will apply to A. quadrans. 



5. Fectenfuscus. Prof. Verrill may be right in stating that 

 this is the young of P. tetmicostatus and not of P. irradians. 

 I judged otherwise from the description of the first-named 

 species in Gould's work. 



6. Dentalium dentale^ Gould. I admit that this may be 

 specifically, but not generically, distinct from D. striolatum. 



7. Dentalium striolatum. Having examined and carefully 

 compared numerous specimens of this shell and D. ahyssorum^ 

 I have no hesitation in considering them the same species. 

 All have a terminal pipe (as in D. dentalis), which is partly 

 slit (as in D. entalis), so as to connect Dentalium with the so- 

 called genus Entails. 



8. Crepidula plana. If Prof. Verrill has found this species 

 on the outside of other univalve shells or other substances in 

 company with typical specimens of C. fornicata, and there is no 

 intermediate form, I agree that they may be different species. 



9. Margarita acuminata. Probably distinct from M. varicosa. 

 As to the alleged errors of nomenclature, my answer is 



this : — 



j^olis salmonacea and jE. gymnota. Couthouy certainly 

 described both before Dekay ; and the names of the former 

 must therefore stand for these species. 



