40 LEPAS. 



between the shell and the man, is that one is a passen- 

 ger on the outside of the vessel, and the other within. 



The figure given by Chemnitz under the name of 

 Tulipa alba, is merely a white variety of this shell. It is 

 remarkable for its size, which is very considerable, but 

 differs in no other respect. This white variety has been 

 dredged up in the neighbourhood of the Feroe Islands, 

 at the depth of forty fathoms. The want of colour is 

 probably owing to its situation in the deep, for why 

 should not the colour of shells, like that of plants, 

 depend on the influence of the rays of light? Those 

 which are naturally coloured, may lose much of their 

 beauty when they grow at too great a depth, and 

 become quite white when they are wholly beyond the 

 reach of the solar rays. 



The figures of this shell by Gualtieri are very indif- 

 ferent. 



Gmelin's L, tulipa, p. 3209, No. 9, and L. cylindrica, 

 p. 3213, No. 25, are repetitions of this species. 



SCOTTISH ACORN. 

 PL 6. /. 3. Mr. Sowerby. 



6. Lepas Scotica. L. testa sexvalvi, conica; valvulis longitudinaliter 



costatis. 

 Shell conic, of six valves; valves ribbed longitudinally. 



This species, which was found in Scotland fixed to the 

 Mytilus Modiolus, has six raised unequal, triangular 

 valves, ribbed longitudinally, and striated at the base 

 transversely. The operculum resembles that of the 

 L. Tintinabulum. The shell is of a sordid white colour, 

 tending to greenish. 



