192 SYSTEMATIC ARRANGEMENT 



less ; gill exposed ; foot oblong, transverse, very large, sides foldec 



on the back. Teeth ? Shell none. 



" Mouth a linear longitudinal slit ; genital pore in front and vem 

 behind ; the gill composed of many plumules, partly covered by i 

 fold of the mantle." — Philippi, Moll. Sicil. 97. 



1. G. Meckelii,t. 60*. f.8; t. 131. f. 1. (Clio amata), t. 132. f. 1-10 



2. Posterobranch^a. 



Head-disk short, truncated behind. Eyes none. Body and man- 

 tle oblong, shell-less, convex, with a triangular bifid posterior process. 

 Foot very broad, oblong, rounded. Teeth ? Shell none. 



1. P. maculata, t. 168. f. 2. 



The animal requires re-examination. M. d'Orbigny ealls what I 

 have here considered the head-disk and the body, the front and 

 hinder portion of the foot, which, he says, unlike any other mollusk, 

 is divided transversely in half into two very distinct portions. If the 

 above theory is correct, the foot is spotted, and the upper part of the 

 body is one-coloured ; but the foot of several Aplysice is spotted and 

 variegated. 



Messrs. Adams have referred this genus to the Bullidce, but they 

 have taken the front part of the mantle (of M. d'Orbigny) for a 

 cephalic disk, though M. d'Orbigny particularly described the mantle 

 as being continuous, and have made their figure to agree with this 

 theory, representing it as divided into two distinct portions (see Gen. 

 Moll. t. 58. f. 5). 



** Shell distinct, covered. Gill on right side. 



' 3. DORIDIUM. 



Head-disk ovate, truncate behind. Eyes none ? Body depressed, 

 truncated behind. Mantle large, oblong, shorter than the expanded 

 foot. Shell covered, thin, flat, triangular, 



1. D. marmoratum, 1. 131. f. 2, 3. Eidothea ma.rraova.ta, Risso (Eur. 



M&rid.t. 1. f. 17). 



2. D. Meckelii, t. 132. f. 1, 1 a. 



4. Philine. 

 Head-disk trapeziform, elongate. Eyes none. Mantle moderate, 

 bluntly notched behind. Foot broad ; side lobes large and fleshy, 

 reflexed, edging the head and front of the mantle. Shell concealed, 

 thin, fragile, ovate, convolute ; spire small ; aperture very large, 

 open. 



1. P. aperta, t. 60. f. 5, t. 60*. f. 2, t. 132. f. 6, t. 175. f. 6 ; Forbes 



8f Hanley, B.M. t. V.V. f. 1. 



2. P. , n. s., t. 175. f. 5. Borneo. 



3. P. , n. s., t. 132. f. 4. West Indies. 



