Mr. W. Clark on Caecum trachea and C. glabrum. 181 



side of which, at the usual point, may be seen a minute pale red 

 branchial leaflet which puts on the appearance of there being 

 two, a large and a smaller one, as in. the canaliferous Gasteropoda ; 

 but here, though we cannot vouch that there are not two, we are 

 inclined to think there is only one, with a divergence from its 

 base of a part of its surface ; the very marked canal seems neces- 

 sary for the entrance of the branchial water, in consequence of 

 the neck of the animal, when at rest, being so closely embraced 

 by the fleshy muscular circular mantle, but in marching order it 

 is protruded to an extraordinary extent. 



The stomach was distinctly observed, and is an oblong bursi- 

 form organ, yellowish white and granular without, but on being 

 opened presents a dark lead-coloured cavity, fortified by strong 

 transverse muscular bands or fillets. From it arises a very long 

 convoluted intestine, and when extracted exhibited the usual fsecal 

 matters; it appeared to coast the liver and ovarium, amongst 

 the folds of which it makes a double, as is usual with the regular 

 Gasteropods, then progresses to the right side, where the minute, 

 elongated, oval, conically pointed pellets were observed to be 

 ejected. 



The ovarium is dark red-brown, aspersed with the most minute 

 darker points, like the finest sand, with its posterior extremity 

 fixed in the hollowed-out chamber of the terminal process of the 

 shell ; it then extends to the stomach accompanied by the liver 

 in alternate transverse portions ; this organ is a light greenish 

 mass formed of larger granules than the ovarium, and the con- 

 trast in colour of the two substances caused them to be observed 

 without difficulty. 



The neck admitted of a close examination, and did not exhibit 

 the slightest traces of external reproductive organs; it would 

 then appear that the animal must depend on its own influences, 

 but there are doubts ; and from the concordance of all its organs 

 with a large class of the Pectinibranchous Gasteropods, it may, 

 like them, be unisexual, though the organs have escaped detec- 

 tion ; but in all the specimens examined the ovarium was present 

 in the usual place, and in no instance appeared to be replaced by 

 the testicle, but the discriminations of such minute organs can- 

 not be depended on. 



The foot is short, narrow, and truncate anteriorly when in ac- 

 tion, sloping postcally to an obtusely pointed or rather rounded 

 termination, on the upper part of which end is fixed the strong, 

 circular, corneous, black-brown operculum, smooth and conical on 

 the surface attached to the foot, concave without, and from its 

 centre seven or eight fine close-set spiral lines, not concentrical, 

 fill up the area. 



The animal is not at all shy ; it shows itself in all directions, 



