66 JOURNAL OF CONCHOI.OGY, VOL. I4, NO. 3, JULY, I9I3. 



collapsed condition in which it arrives on our coasts. My largest 

 Torbay specimen of the shell is 2in. by 2in., and from Guernsey 2in, 

 by i|in. The animal of the former, when crawling, was the size of a 

 cucumber a foot long, aiid when at rest lumped as large as my 

 doubled fists. 



In the respective number of rows of teeth in the two species, 

 quoted by Gwyn Jeffreys on the authority of Mr. Jabez Hogg,-' there 

 is an error of transposition ; it is A. depilans that has 70 rows, and 

 A. punctata 40, instead of vice versa. For an account of the 

 dentition oi A. depilans, vide A. R. Hunt, Trans. Devon Assoc, 1877, 



PP- ^-Z- 



An Aplysia from Polperro, Cornwall, has been described as A. 

 fnelanopus Couch, '^ but I consider it a very doubtful species. 



Pleurobranchus membranaceus Mont. — Jersey (Duprey and 

 J.T.M.); Scilly (Smart)! Isle of Man, not uncommon (Herdman); 

 off Cumbrae (Norman). It is also said to have been " frequently 

 taken " in the Clyde by the yacht ' Medusa.' 



This is a gregarious species, appearing only at intervals, and some- 

 times in great numbers; I have known quite 100 obtained in one 

 haul of the trawl. In 1874 a large fleet of them appeared simulta- 

 neously at Weymouth and Torbay, and again in the latter district in 

 1877 and 1887. The animal is not "thick," as stated by Jeffreys, 

 but gelatinous and watery, and if left for a few days exposed on the 

 beach dissolves away like the Medusa. There is no doubt of its 

 mantle containing spicules similar to those in the Nudibranchiata, as 

 the handhng of them for any length of time produces blistering and 

 scarifying at the tips of the fingers, similar to the action of a strong 

 acid. The same effects are produced by handling that fine nudi- 

 branch Triiojiia honibergi, which occurs with it in South Devon. 

 The shell is usually oblong, but sometimes approaches an oval; it is 

 highly iridescent, and occasionally pearl-white. According to Pilsbry, 

 P. }ne?nbranaceus Mont. (181 1) is subsequent to 7*. tuberculatus 

 Meckel (1808). 



P. plumula Mont. — Jersey (Duprey and J.T.M.) ; Scilly Islands 

 (Smart and others) ; Penzance, Borough Island, Torbay, Weymouth, 

 Killala Bay. 



var. alba Marsh., Journ. of Conch., 1893, ^^\ ^'^^•1 P- 265. — 

 Bordeaux Harbour, Guernsey (Tomlin) ; Jersey and Scilly. 



This species has a much more substantial shell than the last, but 

 is extremely brittle. Very young ones are occasionally found in 

 shellsand, and resemble a bleached Otina oiis ; but the latter is more 

 convex, with a longer spire, and tiie circumference of the aperture is 



1 Bi-it. Conch., vol. v., p. S. 



2 Pioc. Zool. Soc, 1S70, pp. 173-5 'with woodcuts). 



