34 TESTACEA. 



Patella tessellata. — Plate \^II., Figs. 5, 6, 7. 



The specimens of this animal, when j'oung, are apparently of a 

 regular oval form. The vertex of the shell is white, and four red rays 

 diverge down to the margin of the upper surface. That of the under 

 surface broadens, as is seen in some of the Patella tribe. It is tesselate, 

 or composed of alternate dark and light parallelograms. 



The animal is dingy white : the head broad and distinct. 



Plate VII. 



Fig. 5. Patella tessellata. 



6. Tlie same, enlarged. 



7. Under surface. 



The vivid colours decorating such shells are not only liable to fade, 

 but perhaps they merge in others, so as to render the accurate discrimi- 

 nation of species very precarious. Hence, some which are concluded to 

 be distinct species, may be in fact only varieties. Some I have preserved 

 a considerable time, without being sensible of their increment, which 

 augments the perplexity. 



It appears that the animals of the Patella tvihe derive their suste- 

 nance from very scanty vegetable products. Perhaps they may consume 

 harder substances. 



Patella ?— Plate VII., Figs. 8, 9. 



This is placed here provisionally. Before an accurate description of 

 it was made, but after a good drawing, it was lost accidentally. 



Diameter of the shell about four lines ; colour greyish brown. 



Animal a Limax, Hght grey : a black eye at the exterior root of 

 each of its two tcntacula. Marine. 



Plate VII. 



Fig. 8. Shell, with the animal. 

 9. Empty shell. 



