Umbrae u! n in.] GASTROPODA. 549 



1. Umbraculum umbellum, Marty n, 1786. Plate 23, fig. 14. 



Patella umbella, Martyn, Un. Conch., iii, pi. 102, 1786. P. sinica, Gmelin, 

 Svst. Nat., ed. xiii, 1790, 3705. Umbraculum sinicum, Gmel., Man. 

 Conch. (1), xvi, 180, pi. 70, f. 58-60 ; pi. 71, f. 63-65 ; pi. 72, f. 70, 71. 

 Patella umbella, Gmelin, I.e., 3706. P. umbella ta, Gmel., I.e., 3720. 

 Acardo umbella, Lam., Syst. A.s.V., 1801, 130. A. orbicularis, Miihlfeldt, 

 Ber. Gesellsch. Naturf. Fr. Berlin, 1811, 63. Untbraculum chinense, 

 Schumacher, Essai Nouv. Syst., 1817, 178. Umbrella indica, Lamarck, 

 A.s.V., vi, 1819, 343. Ombrella indica, Blainville, Man. Conch., 475, 

 pi. 44, f. 1. Gastroplax tuberculosus, Blainville, Diet. Sci. Nat., xviii, 

 177. Operculatum aurantium, Pease, Amer. Journ. Conch., iii, 287. 



Shell large, oval, inequilateral, depressed. White under a thin 

 straw-coloured cuticle, which is lamellose and brownish toward the 

 periphery. Vertex a small conical yellow boss, behind the middle 

 and decidedly nearer the left side, apex recurved. Disc with growth- 

 lines and numerous very low unequal radial waves, the margin but 

 slightly undulating. Interior brown and conspicuously radially striate 

 inside the muscular scar ; white toward the edge. 



Breadth, 70mm.; length, 88mm.; height, 11 mm. Breadth, 

 57 mm. ; length, 75 mm. ; height, 11 mm. (Bay of Islands). Breadth, 

 42 mm. ; length, 51 mm. ; height, 8 mm. (Kermadec Islands). 



Type lost. 



Hob. Bay of Islands (J. C. Anderson) ; Kermadec Islands (Captain 

 Bollons). The species occurs from East Africa to the Hawaiian Islands. 



Remarks. It is said that the late Mr. Grosch found a living speci- 

 men of an Umbraculum north of Auckland, and the shell ought to 

 be in the Strassburg Museum. I wrote to the Director of the 

 Museum, asking for some information on the specimen, but I never 

 got a reply to my letter. 



Fam. PLEUROBRANCHIB.E, Gray. 



Animal with the inferior tentacles forming a frontal veil ; the gill- 

 plume arises about the middle of the right side and extends backward ; 

 the dorsal shield is fleshy, stiffened by spicules, and either shell-less, 

 or concealing wholly or mainly a delicate haliotiform shell. The 

 radula is multiserial, without rachidian teeth, and the jaws are well 

 developed, composed of many oblong plates arranged in tessellated 

 pattern ; rhinophores present. 



The family is world-wide in distribution in tropical and temperate 

 (rarely in cold) seas. 



KEY TO GENERA. 



A. Mantle with the edge free and overhanging on all sides ; 



rhinophores close together, inserted below anterior 

 edge of mantle on the frontal veil. Shell wholly 

 immersed in the closed mantle. Verge or its foramen 

 close to female orifice . . . . . . . . PLEUROBRAXCHTJS. 



B . Mantle passing without boundary into the broad anterior 



veil, the rhinophores far apart, inserted on the sur- 

 face of united mantle and veil ; no shell. Posterior 

 and left borders of mantle passing directly into the 

 integument of the foot, not free . . . . PLEUROBRANCH.EA. 



