G6 RESEARCHES TPON THE HYDROBIINjE 



cut (Fig. 28) of that of Sayana, copied from Troschel's work, 

 with that of the lapidaria as given above. The difference in the 

 deuticulation of the lateral teeth is indeed considerable, but can 

 scarcely be considered generic, in the absence of other important 

 distinctive characters. 



Before .concluding our remarks upon this subfamily, we must 

 not fail to allude to the very close resemblance to Fomatioj^^sis 

 shown in the genus Tomicliia of Benson, which is placed by most 

 writers among the air-breathing snails, of the order Operculata, 

 sul)orderOpisophthalma, and family TruncatellidiE. In this animal 

 the shell is extremely similar to that of Pomatiopsis, and the foot is 

 also provided with lateral sinuses. It is said to live in fresh-water 

 ditches. " The adult specimens, for the most part, crept about 

 on the moist earth at the edge of the water ; but the younger 

 individuals were immersed."^ Such habits would seem to indi- 

 cate a branchiferous rather than a pulmoniferous mode of respira- 

 tion, in the young at least. But the eyes are said to be placed 

 on tubercles near the upper bases of the tentacles, whereas in 

 Pomatiopsis they are at the outer bases. The superior position 

 of the eyes may be of itself of little importance ; but it is found, in 

 other cases to be co-existent with respiratory organs formed for 

 breathing air. The lingual dentition, as figured by Troschel,^ is 

 similar to that of Foniaiiopsis in all respects except that the 

 rhachidian tooth has its basal denticles connected by a transverse 

 plate ; — a character wdiich approximates it to the Truncatellidae. 

 Troschel places Tomicliia in the same group with Liihoglyjjhus, 

 upon what grounds it is not easy to comprehend. 



"Whatever conclusions may be arrived at from these facts, we 

 have undoubtedly here, between Tomicliia and Pomatiopsis, the 

 closest point of osculation between the branchiferous and pulmo- 

 niferous Gasteropods. 



Three genera have been recently described in the " Annals and 

 Magazine of Natural History," which have considerable resem- 

 blance in form or habits, or in both, to the Pomatiopsinae. These 

 are Cecina,^ A. Adams ; Blanfordia* A. Adams, and Cremno- 



' Benson, Ann. and Mag. Nat. Hist. [3], XII, (1863,) 424. 



^ Gebiss der Schnecken, I, pi. vii, fig. 15. 



8 Ann. and Mag. Nat. Hist. [3], VIII, (1861,) 308. 



* Ann. cit. [3], XII, (1863,) 424, pi. vii, fig. 11, 12. 



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