OF MOLLUSCA. 1 17 



to have ribs corresponding to those of the Pecten. When found in 

 the cavities of shells, it is white, flat, with a convex diaphragm ; the 

 younger specimens are rounded, but generally become elongated by 

 age ; and it is otherwise very variable in shape, conforming itself to 

 the position it occupies in the throat of the shell. When found 

 among stones at the roots of sea-weed, it is generally of a small size, 

 with a convex diaphragm. 



Crepidula dilatata changes its form and character according to the 

 body to which it happens to be fixed : — 



1- If attached to a broad stone or other body, the shell is smooth, 

 circular or ovate and moderately convex ; it is then C. dilatata, 

 C. peruviana, C. depressa, C. patula, C. lineolata, C. Adolphcei, 

 C. chilensis, and C. strigata. 



2. On the contrary, if fixed to a small round stone, and the shells 

 are obliged to group themselves on one another, it is then narrow, 

 very convex, and C. nautiloides. 



3. When the young shell happens to be in deeper water, and 

 fixes itself between the roots of sea plants, it becomes irregular, 

 thick, and of a uniform colour ; it is then C. pallida. 



4. If it happens to be fixed on the inside of a dead spiral shell, 

 especially if that shell is inhabited by a Soldier crab, it becomes flat 

 or even concave externally, and is of a white colour ; it is then C. 

 plana or C. unguiformis. 



Crepidula patagonica and C. aculeata occur attached to stones 

 on the coast of South America ; the former often chooses situations 

 much beaten by the waves. 



Crepidula dilatata forms large rounded massive groups, the lower 

 shell being attached to a stone or shell, and the others all placed 

 on the back of it. 



2. Garnotia. 



Shell oval, convex, covered with a smooth periostraca ; apex me- 

 dial, posterior, distant from the base; inner lip deep within the 

 cavity, shelving downwards in front. 



1. G. solida, Hinds, Fog. Sulph. 53. t. 14. f. 7, 8. G. rostriformis, 

 Gould, Eocped. Shell, 14. 



Living attached to the outside of shells. 



b. Galerina. Foot naked. Shell subspiral. Body and shell conic, 

 subspiral; apex of the shell superior, subcentral ; inner plate 

 of the shell subspiral, ascending obliquely. 



3. Galertjs. 



Shell subconic ; inner lip subspiral, oblique. 



1 . G. chinensis, 1. 1 30. f. 1 ; Forbes $• Hanley, B. M. t. B.B. f. 8-1 3. 

 (young shell spiral, f. 10, 11); Adams, Gen. Moll. t. 40. f. 6. 



Central tooth of Galerus sinensis wider at the base ; cutting 

 edge triangular, serrated. Lateral teeth : first with the tip wide and 



