156 LITTORINID^. 



ulate tentacles bearing the eyes on bulgings at their 

 external bases. Foot rather short, oblong, rounded at 

 both ends ; operculigerous lobe with rudimentary lateral 

 wings, and furnished posteriorly with an obscure rudimen- 

 tary cirrhus. 



This genus was established by Dr. Fleming for the 

 Helix depressa of Montagu, and some apparently allied 

 shells, and was dedicated by him to the memory of Dr. 

 Skene, of Aberdeen, a Scottish naturalist of eminence in 

 the time of Linnneus. It is synonymous with the Del-plhi- 

 Qioidea of Brown, The BJceneee, may be said to be discoid 

 Rissoa. The on!}' one of the following shells which un- 

 questionably should retain this generic appellation is the 

 S. planorbis, type of the genus. All the remainder are 

 doubtfully, and in the absence of information respecting 

 their animals, placed here. Indeed, there is good reason 

 to surmise that they do not even belong to this family, but 

 are rather likely to prove Trochida, and some of them, at 

 least, are, in all probability either belonging or nearly allied 

 to Adeorhis. At present, however, we prefer describing 

 them under the genus the shell of which they most re- 

 semble. Philippi has placed some allied forms in Del- 

 phimda with a query. That genus is very nearly allied 

 by both aninuil and shell to Trochus. 



S. PLANORBIS, O. Fabricius. 



Pale olivaceous or brown, devoid of sculpture, not lustrous, 

 suture subcanaliculated ; umbilicus not ribbed ; aperture almost 

 circular. 



Plate LX XIV. fig. 1, 2, 3 ; and (Animal) Plate G. G. fig. 1. 



Turho phinorbis, 0. Fabr. Fauna Gioenland, p. ,394, from which GiMEi., Sjst. 

 Nat, p. 3602, 



