212 On the Mollusca of Europe and North America. 



1838, from whom Dekay borrowed both the descriptions and 

 figures live years later. 



He states that DentaUum dentale (non Linn.) is a variety 

 of Entalis striolata, and that the latter is a variety of D. 

 abyssorumj Sars ; but both of these statements are incorrect. 

 The first is the DentaUum occidentale, Stimpson, and is a true 

 DentaUum^ entirely different, generically and specifically, from 

 the striolata] and the latter is also quite distinct from ahyssorum. 

 Possibly Mr. Jeffreys has not seen perfect specimens of all the 

 American species ; otherwise I cannot understand how he could 

 have made these statements. 



He is correct in considering Crepidida glauca a variety 

 of C. fornicata^ as others have done before him ; but he has 

 adopted a serious mistake, made by several other writers, in 

 regarding C. plana (or tinguiformis) also as a variety of C. 

 fornicataj from which it is really very distinct. It is a very 

 common error to suppose that this species always inhabits the 

 inside of dead univalve shells ; for it very often occurs on the 

 outside of such shells, on stones, the back of Limulus, &c., 

 and is frequently associated intimately with fornicata in all 

 these situations ; but nevertheless it always retains its essential 

 characters under all circumstances. The typical _/or?^^cato is 

 also often found with it, plentifully, on the inside of dead 

 shells. 



Nor can Margarita acuminata be the young of M. varicosa ; 

 for in our collection there are full-grown specimens of both, 

 equal in size, from Labrador. 



There is no sufficient reason for adopting the name Lacuna 

 divaricata in place of L. vincta ; for it is not the Trochus divari- 

 catus of Linnd (1767), although it is the shell described under 

 the same name by Fabricius in 1780, as shown long ago by 

 Dr. Stimpson and others. Fabricius made a mistake which 

 we have no right to perpetuate ; nor does " usage," to which 

 Mr. Jeff'reys so often appeals, sanction the change. 



The Lunatia triseriata is not, as Mr. Jeffreys thinks, the 

 young of L. heros^ but only a colour- variety, as the Avriter had 

 previously shown (April 1872). Both varieties occur together, 

 from the smallest to the largest sizes ; but the former some- 

 times becomes plain-coloured before reaching maturity. There 

 is no evidence that Natica claitsa is the Nerita affinis of 

 Gmelin, but quite the contrary ; for the latter was placed in the 

 section of umhilicated species, was described as silvery xoithin^ 

 and came from New Zealand ! It is probably one of the 

 Trochid*, and certainly could not have been this imperforate 

 Natica. 



In this place I sliall not enter into a discussion of te 



