42 Mr. A. Adams on MoUusca from the Cape. 



lamina. The head-lobes are very large and rounded, with the 

 front edge crenulate; the eye-pedicel is large, thick, and tri- 

 angular, with a small, simple eye placed on the outer side near 

 (but not on) the tip ; the neck-lappet is very large, occupying 

 two-thirds of the length of the lateral membrane, the free 

 edge deeply divided and pectinate, some of the divisions 

 again divided at the end, or compound, as seen in Livona pica, 

 the others smaller and simple. The edge of the lateral mem- 

 brane is pectinate, and there is a single, long, stout, white, 

 tentacular filament at the extreme hinder part. The opercular 

 mantle, as in this instance it may appropriately be called, is 

 furnished with three very short conical processes on each side, 

 while the front edge is capable of being extended backwards 

 over the entire rough outer sui-face of the operculum, with the 

 exception of a small portion posteriorly, which is free from the 

 foot below. 



The animals of three species of Oxystele which I have observed 

 here, namely O. tigrina, 0. merula, and O. tabularis, do not 

 differ from each other in any essential respect. They are 

 black, with the head transversely lineated with white ; the head- 

 lobes are simple and triangular ; the long filiform tentacles are 

 barred with white ; the neck-lappets are moderate ; the lateral 

 membrane is finely crenulated, and is furnished with three equal 

 filaments on each side, marked, like the tentacles, with white and 

 black, and the sides of the foot are speckled with white. 



In my excursions among the rocks I was much struck with 

 the rich variety of Patellae, and seized the opportunity of ex- 

 amining the animal of Helcion pectinatus, which has the gills 

 arranged round the groove between the mantle and foot exactly 

 as in Patella, the animal of which it resembles in every respect. 

 Helcion will therefore form a section of Patella, as Dr. Gray 

 suggests, and not a genus of Tecturida, as supposed by my 

 brother and myself in our ' Genera of Recent Mollusca,^ p. 460. 

 The animal of the Cajjc Nacella does not differ from that of the 

 British N. ccerulea. The smooth, thin shell is only found on 

 smooth, rounded stones. The Patella cochlearis has the head and 

 neck very elongated, and resting in the gutter of the narrow 

 fore part of the shell; the mantle is also produced in front over 

 the head. This species forms the subgenus Olana, H.& A. Adams. 

 The stellate forms of Patella forming the subgenus Scutellastra, 

 H. & A. xldams, have the margin of the mantle extended into 

 the radiating processes of the shell. The Patella compressa is 

 also found here, but I have not succeeded in taking it alive. 



I remain. Gentlemen, 



Yours very truly, 



Arthur Adams. 



