VOL. L.] . PHILOSOPHICAL TRANSACTIONS. 225 



than in the lungs, which have nerves from the 8th pair, and from the intercostals 

 improperly so called. 



hXXFl. A remarkable Instance of Four Rough Stones y discovered in a Human 

 Urinary Bladder ^ contrary to the received Opinion \ and Successfully Ex- 

 tracted by the Lateral Method of Cutting for the Stone. By Mr. Joseph 

 Warner, F. R. 5. p. 579- 



[Reprinted in this author's work, entitled Cases in Surgery, to which the 

 chirurgical practitioner is referred.] 



LXXFll. Observations on the Limax non cochleata Purpur ferens, the naked 

 Snail producing Purple.* By J. A. Peyssonel, M. D., F. R. S, Translated 

 from the French, p. 585. 



Among the fish met with in the seas of the Antilles of America, this, here 

 described, appears precious from the beautiful purple colour it produces, in the 

 same manner that the cuttle-fish produces its ink, if n.eans could be found to 

 procure this liquor in a sufficient quantity to render it an article of commerce. 

 These fishes are soft, viscous, without shells, scales, or bones ; are of the na- 

 ture of the polypi, and such other kinds, without feet, fins, or any thing to 

 supply their places. Their motion is vermicular ; and like the slugs they wreath 

 themselves up, and when touched make themselves quite round. They fill up 

 certain membranes of the body with water. Their local motion, antennae, 

 which they lengthen and contract ; and a great many other properties which 

 they have in common with snails, slugs, and turbinated shell-fish, made Dr. P. 

 call them naked snails : and though they have not the most essential qualities of 

 snails, he thought he might give them the name, as they have no particular ap- 

 pellation in this country. Some call them piss-a-beds, some sea- cats, and others 

 a less modest name, tapecon, taken from Pliny. 



This fish is commonly 4 inches long, and 1 thick ; of a greenish colour, 

 spotted with black, each of which forms a circle. The under part is like that 

 of snails, flat, with kinds of mamillae, or rugosities, which are adhesive ; by 

 means of which they advance in a vermicular motion ; and when touched be- 

 come round, by retracting their neck and head ; and afterwards protrude them 

 considerably, according to their motion and progression, crawling upon rocks to 

 seek their food. The head of this animal has a flatness, or is inclinable to a 

 souare or parallelogram. On each side there are membranes of skins, which 

 form kinds of ears ; and under them others, which at times fill with water, and 

 are then transparent. Under this thick skin there is a cranium, of a kind of 



* The animal here described seems to be a species of aplysia. 

 VOL. XI. G G 



