a Genus of quasiparasitic Mollusks. 323 



After the English version of these characters, a few more 

 particulars are given, — viz. that the mantle is of a green hue, 

 and has a small aperture at its base, and that on its ventral 

 aspect is the rudiment of a foot. It is likewise mentioned that 

 " Mr. Cuming found this elegant parasite burrowed in diflFerent 

 parts of the rays of the oral disk of Asterias Solaris. It is 

 almost hidden from sight, so deeply does the animal penetrate 

 into the substance of the Starfish, in which it makes a comfort- 

 able cyst for itself, wherein it most probably turns by the aid of 

 its rudimentary foot. All the specimens infested with Styliferi 

 appeared to be in the best health. Though there is reason to be- 

 lieve that they feed upon the juices of the Starfish, with that 

 instinct of self-preservation imparted to all parasites, whose ex- 

 istence depends upon that of their nidus, the Stijlifer, like the 

 Ichneumon among insects, appears to avoid the vital parts ; for 

 in no instance did Mr. Cuming find it imbedded anywhere save 

 in the rays, though some had penetrated at their base, and very 

 near the pelvis/' I must confess that I am not prepared to 

 adopt this teleological mode of reasoning, so far as regards the 

 Stili/er; becau-^^e it does not appear that the Starfish has, in the 

 calcareous and solid parts inhabited by its so-called parasite, any 

 internal juices or soft tissue on which the latter can feed. The 

 investing membrane is wholly external. Although the above 

 description of the animal was undoubtedly correct and circum- 

 stantial, it must not be forgotten that it was drawn up from 

 specimens which had been preserved for a considerable time in 

 spirits. The examination of such specimens could not yield 

 the same result, in a scientific point of view, as that of living 

 individuals in their native habitat. 



Our best British nuilacologist, Mr. Alder, is the only one who 

 has noticed the animal of S. Turtoni. The specimen which he 

 examined was rather injured, and in a very sickly state. He 

 says, " It was white, had a rather large foot, without operculum, 

 and a rounded head with two cylindrical tentacles, and minute 

 eyes at the (external or posterior) base. No portion of the shell 

 was covered by the fleshy parts ; but we are not prepared to say 

 that, in a state of vigour, the animal has not the power of extend- 

 ing some part of the mantle or foot over it. The remains of the 

 animal, examined under a microscope, did not show any denticu- 

 lated tongue." (I may add, by way of parenthesis, that Mr. Alder 

 has, within the last few days, examined the soft parts of two 

 more individuals which I sent him for that purpose, but failed 

 to detect any traces of a spinous tongue.) He also observed 

 that " the otolites are circular, with a central dot, that the gill 

 consists of a single series of triangular lobes, and that the mouth 

 ° 21* 



