a Genus of quasiparasitic Mollusks. 327 
tongue in Stilifer Turtoni, strengthens the supposition that its 
food consists of extremely soft or semifluid matter, and not of 
organisms which have any degree of solidity. Dentalium, which 
preys on Foraminifera and other minute animals, has (according 
. to Lacaze-Duthiers) a very complicated lingual apparatus ; and 
even the little Rissoa, which feeds on seaweeds, often of the 
most delicate and filmy texture, possesses a pair of horny jaws 
and a tongue armed with a strong central tooth, which is flanked 
on each side by a formidable row of serrated lateral teeth. Sti- 
lifer has no jaw or tooth of any kind. 
The late Mr. Stewart, of the College of Surgeons (whose un- 
timely death is still deplored by all who study the British Kehi- 
nodermata), was of opinion that Stilifer Turtont infested Echint 
for the sole purpose of depositing its spawn. We know, from 
the observations of Mr. Peach, that Lamellaria perspicua fre- 
quents the shore at Wick, between tide-marks, every summer, 
and makes a nidus for its spawn in a species of Botryllus. But 
Lamellaria is not, like Stilifer, restricted to a particular habitat. 
The former attaches itself to the under side of loose stones, and 
is also found generally distributed over the sea-bed, except per- 
haps im the spawning-season. The Hchini on which Stilfer 
Turtoni have been taken are very rarely covered with spawn; 
and Stilifers of all ages, from one to half-a-dozen, occur on 
Echini, but nowhere else. 
The fecundity of Stilifer is very great ; and it therefore ought 
not to be a rare shell. I counted at least 100 fry in one of the 
clusters of spawn on the back of the Shetland sea-egg ; and as 
there were 41 of these clusters, this would yield a prospective 
harvest of more than 4000 specimens—enough to supply almost 
all the conchologists in the world. Moreover one of the adult 
Stilifers appeared to be full of spawn. As the Echinus probably 
could not accommodate more than half a dozen Stilifers when 
they came to maturity, what would have become of the rest, 
supposing any of them escaped being the prey of other animals? 
Would they migrate, and form colonies on other Echini? They 
have feet and eyes; and suitable habitations are not wanting in 
the same part of the sea-bed where I procured the specimen 
which have given rise to the above remarks. 
Various have been the positions which conchologists have 
from time to time, assigned to this remarkable mollusk im their 
systems of classification. Turton placed it in Phasianella ; 
Fleming in Velutina, but with doubt; Reeve at first between 
Turritella and Cerithium, but recently between Canalifera and 
his Turbinacea; Macgillivray among his Turbinina, and next to 
Lacuna; Forbes and Hanley, as well as Woodward, in Pyra- 
midellide ; H. & A. Adams as a distinct family between Euli- 
