126 SYSTEMATIC ARRANGEMENT 



II. Protopoda, Gray. 



Foot rudimentary, round, truncated or club-shaped. Shell attached, 

 irregular. Operculum spiral or none (see p. 64). 



Fam. I. VERMETID.E. 



Foot small, folded on itself. Body and shell rather irregularly 

 twisted, attached by the outer surface of the shell. Egg in an ob- 

 long membranaceous sac. Shell of young subspiral, rather irre- 

 gular. 



a. Vermetina. Mantle and shell entire. Operculum single or 

 wanting. 



1. Siphonixjm. 



Operculum large, smooth, circular, concave ; scar central, circular, 

 rugose. 



1. V. maximum, t. 56. f. 5, t. 128. f. 2 ; Adams, Gen. Moll. t. 38. 



f. 7. 



2. V. Tonganum, t. 56. f. 7. 



3. V. reticulatum, t. 56. f. 2. 



4. V. carinatum, t. 56. f. 1. 



5. y.?? ,n. s. t. 82. f. 1. 



2. Vermetus. 



Operculum large, rather concave ; whorls many, thin, with a thin 

 produced external edge ; scar central, circular, with close, regular, 

 concentric grooves. — Adams, Gen. Moll. t. 38. f. 8 a, b. 



1 . V. lumbricalis, Lamk. 



2. V. Hindsii. Irregularly twisted, B. M. 



The pointed end of Vermetus lumbricalis forms a spire of eight or 

 ten closely connected whorls, upon each of which are two sharp ele- 

 vated ridges. It generally lies in a horizontal direction, and is 

 attached by one of its sides to some foreign body. The operculum 

 is horny, circular, with a central nucleus and concentric rings. 



The animal of Vermetus radicula of North America has the mantle 

 fringed at its margin with short filaments. The branchial plume is 

 very large and long, situated nearly over the middle of the back. 

 The foot is very short and broad, dilated into rounded auricles ante- 

 riorly. The muzzle is broad, not cleft ; the tongue small. The 

 tentacles are short, conical, having the eyes at their external bases. 

 An elevated ridge runs along the back, becomes flattened into a 

 membrane at the head, and passes round under the right tentacle, 

 forming a kind of canal, near which is the anus. The operculum is 

 corneous, concentric, black and hard on the inner, and lamellated on 

 the outer surface ; it is surrounded by a thin membranous flexible 

 portion about one-fourth its diameter ; thus it is enabled to close its 

 shell perfectly at the aperture, and yet to retreat far into the nar- 

 rowed whorls. The eggs are deposited in July. The egg-cases are 

 soft, slightly cohering, in the form of an elongated cone bent into a 



