SRENEA. 1C)7 



-? COSTULATA. 



Plate XC. f. 1. 

 Maryariia ? cosiulata, Moller, Index INIoll. Greenland, p. 8 ? 



Almost at the moment of going to press, tliere lias been 

 transmitted to us a single dead (and consequently colour- 

 less) specimen of this strongly-featured shell. Unwilling 

 to omit any indigenous species, and averse to constituting 

 a genus from a single individual (and we know not into 

 what marine genus it would naturally fall), we have provi- 

 sionally appended its description to the assemblage of forms 

 which our present ignorance of the mollusks that inhabit 

 them have compelled us to link together as Skenece. 



It agrees fairly enough with the too succinct description 

 of Holler's Marg. ? costulata, but we will not venture to 

 assert its identity, nor even that it belongs to the same 

 genus. The brevity of definition, affected by many natu- 

 ralists for whose talents we entertain the profoundest 

 respect, although it may suffice to distinguish the species 

 of any one particular district or country from each other, 

 deals not sufficiently with details, to enable the describer 

 of a different Fauna to positively identify the objects they 

 intended to define. Negative characters must occasionally 

 be indicated as well as the more salient positive features. 



The specimen alluded to is very small, very thin and 

 fragile, and of a globosely orbicular shape, with the spire 

 short (though scarcely so for -a Margarita) ^ and the front of 

 the aperture considerably below the basal level. Very 

 numerous and rather wavy flattened folds, that are some- 

 times forked on the penult whorl, and are peculiarly well 



