372 MOLLUSCA. 
This little species is similar to the preceding, but is less elevated, 
and the ribs are more uniform. It is also quite like R. Noachina. 
Figure 478, dorsal view of the shell: 4784, foot of the animal; 4784, 
‘profile of the shell, with the animal; 478 c, head and tentacles in out- 
line, enlarged. 
EXMARGINULA ASPERA ( (ould). 
Testa parva, tenuis, depresso-conica, fuliginosa ; costs elevatis quadratis 
plerumque duplicibus ad decem albidis, ad intervallos striis crebris 
decussantibus exasperatis ; vertice subcentrahi, acuto, recurvo: intus 
glauca, allido-radiata ; margine denticulato: incisura angusta, pro- 
funda, intus in canalem versus apicem producta. 
Emarginula aspera, Gourd; Proceed. Boston Soc. Nat. Hist., 1. 
154. August, 1846. Expedition Shells, 12. 
SHELL small, thin, depressed-conical; apex subcentral, acute, re- 
curved; surface sculptured with ten or twelve principal ribs, which 
are square, and extend beyond the general margin, the four anterior 
ones being much the largest, and double; intervening spaces finely 
grooved with sharp radiating striz, all finely imbricated by very 
numerous distinct lines of growth, rendering the surface like a rasp. 
Colour smoky black. Apex and ribs white; interior bluish-green, 
rayed with white at the ribs. Margin finely serrate, deep green. 
Fissure narrow and deep, with a channel prolonged to the apex. 
Length four-tenths of an inch; breadth three-tenths of an inch; 
height three-twentieths of an inch. 
Obtained at Sydney, New South Wales. 
Much like E. rugosa, Quoy, in size and form, but altogether diffe- 
rent in colour, sculpture, and in the larger size of the notch. 
Figures 493, 493 a, 493d, three views of the shell; 493, details of 
sculpture, enlarged. 
