UMBRACULUM. 177 



the anterior slit. Mantle with thin edge fringed by numerous flat 

 processes. Gill a long plume arising in front under the mantle, and' 

 continued along the right side, its latter end free and bipinnate. 



Radula extremely wide, composed of an enormous number of per- 

 fectly similar, very narrow, needle-like teeth, strongly recurved to- 

 ward their apices, the cusps narrowly lanceolate and smooth. 



Type Umbraculum sinicum Gmel. 



The radula of Umbraculum sinictnii which I examined, has more 

 numerous teeth than any other rnollusk known to me. Among 

 Tectibranchs, Dolabella has a somewhat similar type of teeth, but 

 they are wider and much larger. The general characters of the 

 teeth are as in Pleurobranchidce. 



The name Umbraculum of Schumacher is the earliest tenable de- 

 signation for this group, although it had previously been recognized 

 as a genus distinct from Patellaby Lamarck and Miihlfeld. There 

 are several names anterior to the one commonly known, Umbrella 

 Lam. 



DISTRIBUTION : The genus occurs in tropical and subtropical seas 

 of both hemispheres, and is represented in the Eocene of Europe 

 and America. The U. planulatum Conrad of Jackson, Mississippi, 

 rivals in size the largest recent species. Two Jurassic forms, of 

 doubtful pertinence to the genus, have been described. 



There are but few species, either fossil or recent, and the concho- 

 logical characters separating them are neither very obvious nor of 

 much value. The soft parts of U. mediterraneum and the Sandwich 

 Island form of U. sinicum only are known. 



Species of Umbraculum. 



Panamic region : U. ovalis. 

 An til lean region : U. plicatulum, bermudense. 

 Mediterranean region : U. mediterraneum. 

 Indo-Pacific and U. sinicum, E. Africa to Hawaiian Is. 



[Australian regions: U. cumingi, Reunion Island. 



U. pictiim, Lord Hood's Island. 

 U. corticalis, South Australia. 



U. OVALIS Carpenter. PL 70, fig. 61. 



Shell similar to U. indica, but the margin scarcely undulating ; 

 regularly oval; apex spiral, somewhat projecting, less inequilateral ; 



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