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. Dentatium, which 

 preys on Foraminifera and other minute animak, 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 Echi- 

 nodermata), was of opinion that Stilifer Turtoni infested Echini 

 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 BotnjUus. But 

 Lamelhria 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 in the spawning-season. The Echini on which Stilifer 

 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 

 har>est 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 "i ."^^^V 

 have feet and eyes ; and suitable habitations are not wanting ia 

 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 moUusk in 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- 

 midellida ', H. & A. Adams as a distinct family between Euli- 



