136 BULLETIN OF THE 



due to growth-stages in one or two species, it will become much easier to 

 assign a place to some at present very puzzling forms. 



Olivella (bullula var. ?) tubulata Dall. 



This form varies from moderately stout, or a little more slender than Reeve's 

 figure, to extremely attenuated. It is in the last case about the shape of 

 0. nywpha Adams & Angas, but more cylindrical, pure white, the walls and 

 spire sometimes translucent ; the broader form recalls 0, fioralia (Duclos) 

 Tryon, from the white varieties of which it is at once distinguishable by the 

 large size of its nuclear whorls. The soft parts dried up in one specimen show 

 no sign of an operculum. The slender form is 11.3 mm. long and 3.5 mm. in 

 greatest diameter, with five whorls. The length of the aperture is almost ex- 

 actly half that of the shell. The stouter form is 13.3 mm. long, 5.0 mm. in 

 diameter, with five whorls, and the aperture 8 mm. in length. The suture in 

 both is deeply channelled, except between the two nuclear whorls, which are 

 rounded and flattened on the summit. A specimen was obtained at Station 

 20, in 220 fms., off Cuba, and another by the Fish Commission in 225 fms., 

 off the northeastern end of the same island. 



Family MARGINELLID^. 

 Genus MARGINELLA. 



This group has been absurdly over-divided. The species melt into one an- 

 other, as it were, as soon as plenty of material is brought together ; so that 

 most of the subgenera quietly efface themselves. For the species of the Blake 

 Expedition, which comprise only a small part of those native to the region, I 

 adopt for the occasion the following subgenera : — 



Marginella, with Sections Volvarina and Volutella ; Persicula, with Section 

 Gibberula. 



Marginella apicina Menke. 



Marginella apicina Mke., Syn. Moll., p. 87, 1828. 



Marginella conoidalis Kiener (1840), Auctorum. 



Marginella caribcea Orbigny, Moll. Cuba, XL p. 97, pi. xx. figs. 24-26, 1845. 



Marginella livida Hinds, P. Z. S. 1844, p. 73. 



Marginella Jiavida Redfield, Ann. New York Lye. Nat. Hist., IV. p. 163, pi. x. fig. 4 



a-b, 1846; Cat. Marg., p. 223, 1870. 

 iMarginella borealis Verrill, Trans. Conn. Acad. 



One specimen of this common West Indian form was collected by the Bache 

 in 100 fms., south of Inagua Id., Bahamas, 1872. 



Specimens of undoubted apicina have been collected by the U. S. Fish Com- 

 mission near Cape Hatteras, in 1885, which fact renders it highly probable 

 that Verrill's borealis is at most a northern race of this protean species, or of 

 M. limatula Conrad. The specimens I have seen seem intermediate between 

 these two. 



