TESTACEA. 33 



Patella pellucida. — Plate VII., Figs. 1, 2. 



Shell an irregular ellipse, in the circumference conical, one end 

 broader than the other, of a thin transparent horn colour, with, generally, 

 four interrupted streaks of bright green radiating from the vertex to 

 the margin, with darker intermediate streaks : animal light brown : head 

 and body distinct ; two tapering tentacula, with a black eye at the ex- 

 ternal root of each. The position of the head is under the vertex, or 

 toward the narrow portion of the shell, and the body is covered by the 

 broader portion. The margin of the under surface is environed by a 

 border of short filaments. Specimens have little exceeded half an inch 

 in length, and some, in favourable situations, are said to approach a 

 whole inch. 



This creature occurs on the common Laminaria at low -water mark, 

 whereon it seems to feed. Probably it also derives sustenance from the 

 confervas, or other vegetation covering the rocks. 



It is certainly among the most delicate of its race. 



Plate VII. 



Fig. 1. Upper surface. 

 2. Under surface. 



Patella undata — The Waved Limpet. — Plate VII., Figs. 3, 4. 



As the smaller animals of this genus are most common, they have 

 been less the subject of observation ; their reciprocal relations are uncer- 

 tain ; neither is it evident whether they grow much larger. 



The margin of the shell of the Waved Patella the eighth of an inch 

 in diameter, is somewhat of an elliptical form. Vertex white, with waving 

 lines radiating down to the margin. The animal occupying the shell 

 feeds on the Millepora. Perhaps the specimen represented may be young. 



PL.A.TE VII. 



Fig. S. Patella undata, enlarged. 

 4. Ditto. 



