J. D. MACDONALD ON THE CLASSIFICATION OF THE GASTEROPODA. 77 



point, Na Viti Levi, Feejee group ; and several specimens were selected for examination. 

 The tentacula are stout, conical, and closely approximated above the mouth, with a longi- 

 tudinal groove on their inner surface, and a somewhat sunken eye in a slight elevation or 

 gibbosity at the outer side, near the liase. 



" The animal is furnished with a retractile proboscis of considerable length ; and Avhen 

 retracted, the external aperture is quite round and so small as to lie scarcely perceptible. 

 The anterior border of the foot is dilaminated, the plates or lips being separated l^y a deep 

 transverse recess, which appears to have some communication with the sinus of the foot. 

 The creeping-disk or mesopodium is well developed, and the lateral borders, which are 

 produced into a simple lobe, are probably confluent with the epipodia. Its posterior ex- 

 tremity is very thin, but rounded, and surmounted by the metapodium, which is a sub ■ 

 cylindrical mass of muscular fibres, continuous Avith those of the great retractor, and 

 abruptly truncated posteriorly, where it presents a subcentral recess, which lodges the 

 internally produced nucleus of the paucispiral operculum. 



" The oral teeth form a narrow circular band consisting of a pavement of sharp dental 

 cells, whose points, as in other cases, are directed forwards. 



" The lingual pavement is small, but elongated in form and divided into two lateral 

 arese, supporting several series of long and gracefully curved uncinate teeth, which seem 

 to decrease in length from within towards the lateral borders of the membrane, where they 

 also become bifid in the vertical direction. 



" The auditory sacs are of comparatively large size, containing otoconia. 



" Torinia (Gray). The anatomical characters of this genus (distinguished by the 

 peculiar gun-screw form of the operculum, so much resembling that of Siliquaria) agree 

 in every essential particular with the foregoing. 



" Scalaria. Trom a critical examination of the anatomy of Scalaria, I have no hesi- 

 tation in placing it in the same family with Solarium. Its principal characters are as 

 follow : — Proboscis long, retractile, with stout muscular walls ; the oral aperture furnished 

 with lateral plates, composed of small dental cells vni\\ their points directed forwards. 

 Lino-ual membrane supporting a double pavement of tenaculiform teeth, rather stout, but 

 still very similar to those of Solarium, and not, as has been supposed, lilie those of Bulla. 

 Thus the outer teeth present one or two secondary prongs, while the inner remain simple. 

 The eyes are placed at the outer side of the base of broadly conical tentacula ; and the 

 auditory sacs contain vibrating otoconia. 



" The foot is dilaminated in front, and in general configuration resembles that of Sola- 

 rium.'^ 



Erom the above facts I think it may be affirmed that it is a violation of the simplest 

 anatomical principles to place Scalaria with the TnrritelliclcB, and Solarium with the 

 Litorinidce, the genera in both of which families, as now received, are otherwise hetero- 

 geneous enough. 



The vermetiform character of the animal of Torinia on the one hand, and the peculiar 

 structure of the operculum of Siliquaria on the other (so closely aping that of the former 

 genus), afford some indication that both may belong to the same family. Moreover the 

 o-roove in the outer lip of Solarium would appear to represent the branchial slit of Silt- 



