1. citrinus, Rupp. 



2. comutus, Quo?/. 



3. Forskalii, I). Ch. 



4. luniceps, Ad. 8p R. 



Species. 



5. mamillatus, Quoy. 



6. membranaceus, Mont. 



7. Patagonicus, Orb. 



8. Peronii, Cuv. 



9. plumula, Mont. 



10. punctatus, Quoy. 



11. reticulatus, Rang. 



12. tuberculatus, Z>. Ch. 



Figure. 



Pleurobranchus membranaceus. PL 22. Pig. 129. Shell, of thin semi- 

 transparent membranaceous substance, with its slight marginal apex. 



UMBRELLA, Lamarck. 



Animal ; disc very large and swollen ; tentacles ear-shaped, hav- 

 ing a pair of small sessile eyes between them ; mouth covered 

 with a small, lobed veil ; mantle more or less enclosing a capa- 

 cious, oval, fiat, shelly shield. 



Shell ; orbicular , flat , rather convex at the upper part, with a very 

 small nearly central vertex, rather concave beneath, impressed 

 with a central, callous, yelloio deposit, being surrounded by a 

 regular continuous muscular impression. 



Umbrella is very unlike Pleurobranchus, whether as regards animal or 

 shell ; but in both the branchiae take the form of a plume or row of plumes 

 attached to the right side, while the head is furnished with a veil, and the 

 shell in both genera is invested, or partially invested, by the mantle. Here 

 the resemblance ends. Umbrella is a stout, swollen, warty mollusk, hav- 

 ing a large shell, often of rather solid, calcareous substance, planted flat 

 upon the back, and the inner surface is characterized by a callous deposit 

 of a peculiar yolk-yellow colour. It was known to the older naturalists by 

 the name of ' The Chinese Parasol/ 



Three species are known, varying so little in specific character, so far as 

 the shell is concerned, as to be scarcely distinguishable, but from widely 

 distant localities. One is a native of the tropical Eastern seas, another 

 of the Mediterranean, and the third of the Bay of Panama. 



1. Indica. Lam. 



Species. 

 2. Mediterranea, Lam. 



3. ovalis, Carp. 



