49 



gular golden translucent cusp on the outer base. The whole 

 odontophore enveloped iu a fine golden yellow transparent 

 mombraue, which is cither the intestinal tube or its lining. 

 The odontophore never can be drawn from the animal without 

 this membrane, owing to the long set pointed teeth which 

 hold it in its place. 



Patella ustulata. Beeve Icon. pi. 31, Jif/. 88. If I am 

 right in ray identitication of this shell it must be the same as 

 my P. ta^manica, described in last year's proceedings of this 

 Society. Reeve gives no habitat for his shell, which from ap- 

 pearance was worn and corroded. The unworn specimens 

 found living on the rocks are as different as possible, the ribs 

 and riblets being then conspicuous, and the whole shell a 

 dull yellowish white with no trace of the scorched colouring. 

 When dead, however, and thrown on the beach this feature is 

 conspicuous. It has many fine riblets between the coarse 

 somewhat nodular ribs, and the margin is very finely pec- 

 tinated. A peculiarity of the animal is that it seldom comes 

 above low water mark, and prefers situations where it is much 

 exposed to the waves. It is very stationary, often being sunk 

 into a regular pit in the rock, and appears to live upon the 

 fine green ulva on the rocks. It is nearly always covered, not 

 only with confervoid growths, but also nuUiporae so as to quite 

 alter its shape and appearance. This often alters the height 

 of the shell, which is usually depressed, and changes the 

 position of the apex, which is usually submarginal. The 

 interior is white and the spatula not defined. 



The animal is of uniform pale yellow at the base ; white 

 above the foot, gills semi-pellucid and continued as a delicate 

 fringe all round the mantle. I, however, noticed one exception 

 where, like the former species, the gills were discontinued in 

 front of the head, mantle without tentacles ; head livid, with 

 semi-pellucid tentacles ; eyes very small and at exterior base ; 

 buccal mass red and fleshy ; cartilaginous jaws long and less 

 tumid than most limpets ; odontophore scarcely as long as shell ; 

 not coiled, but bending with intestine in two folds. Teeth 

 closely set and not high, composed of five central small curved 

 cusps, and two tri-lobed laterals, all narrowly tongue-shaped, 

 laterals more acute. The five centrals have the middle tooth 

 often small. Teeth brown, lighter on the summit. 



There are many other Patella known to us from the shells 

 alone, the animals of which I have not examined, viz., P. 

 decora, P. aculeata, P. chapmani, P. radians. Some of these 

 will doubtless prove to be Acmsea. 



GENUS 2.— ACM.EA. 



Animal with a limpet shell, but breathing by a plume-like 

 gill inserted at the back of the head. 



£ 



