212 On the Mollusca of Europe and North America. 



1838, from whom Dekay borrowed both the descriptions and 

 figures five years later. 



He states that Dentalium dentaJe (non Linn.) is a variety 

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

 abyssorum, Sars ; but both of these statements are incorrect. 

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

 Dentalium, entirely different, generically and specifically, from 

 the sti'iolata) and the latter is also quite distinct from abyssorum. 

 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 Crepidula glauca a variety 

 of C. foniicata, as others have done before him ; but he has 

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

 regarding C.])lana (or unguiformis) 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 ij^icdX fornicata 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 5 for it is not the Trochus divari- 

 catus of Linne (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. Jeffi'eys 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 writer 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 clausa is the Nerita affinis of 

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

 section of timbilicated species, was described as silvery within^ 

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

 Trochidfe, and certainly could not have been this imjjerforate 

 Natica. 



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



