156 NASSID Al. 
a callosity at hind-part; outer lip grooved internally, externally 
marginated. B. truncata, Rve. (ii, 76). 
MOLOPOPHORUS, Gabb. Short, robust, spire moderately elevated, 
suture bordered by a more or less distinct carina. Surface 
longitudinally ribbed or striate. Aperture obtuse behind, and 
very slightly notched; outer lip simple, inner lip very slightly 
incrusted, sinuous, anterior notch small, but distinctly defined. 
B. striata, Gabb (ii, 80). Cretaceous; California. 
[BULLIOPsIS, Conr. Placed by its author at first as a subgenus 
of Nassa, it was subsequently removed by him to Melanopside. 
It has some resemblance to Bullia. | 
Nassa, Lam. 
Distr.—131 sp., of world-wide distribution. Fossil, numerous 
species. Eocene—. WN. mutabilis, Linn. (lii, 81). 
Shell ovate, ventricose, body-whorl variously sculptured ; 
aperture ovate, with a short, reflected, truncated, anterior canal ; 
inner lip smooth, often widely spread over with enamel, with a 
posterior callosity or blunt dentiform plait; outer lip dentated, 
internally crenulated. Margin of operculum serrated or entire. 
The animal of Nassa has a broad head, and a foot quadrately 
expanded in front, with the corners often pointed, whilst behind 
it bifurcates and is prolonged frequently into two subulate tails. 
The operculum is usually serrate on the margin, but is sometimes 
plain. The Nasse are very active, and not at all shy when kept 
in confinement. They may be occasionally seen floating with 
the foot upwards. They are predaceous, feeding on other mol- 
lusks, the shells of which they bore. I have frequently seen the 
shells of the American species themselves bored, the hole being 
of such a size as to suggest cannibalism. Perhaps the avenger 
of their misdeeds is a beautiful and very active hermit crab 
which disports itself in the Nassa’s shell, immense multitudes 
being seen at low tide in the water near the shore-line. Whether 
begged, borrowed, stolen, or lawfully captured by the red right 
claw, it is certain that, at Atlantic City, New Jersey, the hermit 
inhabits a vast majority of the specimens of Nassa occurring to 
the collector. Although most of the species are littoral, a ‘few 
have been collected at considerable depths; WN. brychia, ,Watson, 
was dredged at 620 fathoms by the “ Challenger Expedition.” 
Some of them have been observed to spring up “and throw them- 
selves over on being suddenly disturbed. Usually they glide 
along the surface of the mud, leaving a track indicating their 
line of march, at the end of which is a small round pellet; under 
this the creature conceals itself. The fry twist and twirl about 
by means of their ciliated lobes. N. mutabilis is an article of 
food in Italy. The generic name is that of a narrow-necked 
wicker basket used for catching fish, and in such a basket, lob- 
