PROHLIDIUM. 445 



twice the length, and quadruple the area, differed in the 

 following respects, which may, probably enough, depend 

 upon age. The shape was much more depressed, slightly 

 broader, and not so pinched at the sides ; the vertex was 

 blunt, not at all spiral, and much less central. Near the 

 margin the radiating granular striation was the only 

 visible sculpture. 



The animal, which is of sluggish habits, is of a dingy- 

 white colour, and not large in proportion to its shell. The 

 head is turned away from the apex, and is rather small ; 

 it is furnished with two rather short obtuse tentacles, 

 which have no eyes upon their bases. The margin of the 

 mantle is quite plain. The sides of the foot are narrow 

 and the disk of that organ oval. There appear to be two 

 short triangular branchial plumes in the neck-cavity ; the 

 cilia upon them are large. The tongue is very long, 

 and the brown central spines conspicuous, under the 

 microscope resembling bramble-thorns in miniature. 



Propilidium Ancyloide was added to the British Fauna 

 by Mr. Smith, of Jordan Hill and one of the authors 

 of this work when dredging in Lamlash Bay, in 1839. 

 Since then we have taken it alive, in from thirty to ninety 

 fathoms water, off the east coast of Mull ; and, dead, in 

 thirty fathoms, off Lismorc (M'Andrew and E. F.). It 

 has also been found on the west coast, where it was 

 " obtained by Mr. Hyndman, many years ago, on oysters 

 from Strangford Lough" (Thompson). "Two specimens, 

 dredged alive off Ballantrae, Ayrshire, in 1842, were sent 

 me by Mr. Edmund Getty. Dead shells are not un- 

 common among comminuted nullipores dredged at Lamlash, 

 Arran, in 1846, by Major Martin and the Rev. David 

 Landsborougir (W. Thompson). 



