132 BRITISH MOLLUSKS. 



Conovulus (L&uhconia) bidentatus and albus, Gray (1840), Man. p. 227. 

 pi. xii. f. 145. 



Auricula dubia, Cantraine (1840), Bull. Acad. Brux. vol. ii. p. 383. 



Auricula Micheli, Mittre (1841), Rev. Zool. p. 66. 



Ilab. Western and Southern Europe. North, south and south-west of 

 England. Ireland. (In crevices of rocks and timber, among wet 

 moss or under stones, on the banks of rivers near the sea.) 



In this species the teeth are reduced in number to two, and only 

 one of these is conspicuous. The other is an obscure winding basal 

 plate. The shell is mostly paler than that of either of the preceding 

 species, and there is a well-marked variety of shining diaphanous 

 whiteness. It is found on widely remote parts of our coast in the 

 crevices of rocks just above high-water mark, and generally through- 

 out Ireland. 



The testimony in favour of arranging the Conovuli with the 

 Land and Freshwater rather than with the Marine genera, was 

 ably confirmed about twelve years since by the observations on 

 this species of Mr. Clarke. " I think it will be acceptable to mala- 

 cologists," he wrote in a letter to the Annals of Natural History of 

 that date, "to review my notes on the much-disputed point whether 

 the animal respires free air or eliminates it from water by a pectini- 

 branchous organ. Having submitted fourteen live animals to the 

 powers of an excellent microscope, I am enabled to say that I found 

 no traces of a regular pectinated membrane, but when the dissec- 

 tion turned out well, there appeared, as in the usual place of the 

 Helices, what I considered the respiratory cavity, having its walls 

 lined with an anastomosing network of vessels. The animal when 

 put into water instantly escapes therefrom, apparently with the 

 view of breathing air." 



Order II. PULMOBRANCHIATA— breathing both air 



AND WATER. 



Respiratory organ a vascular sac for tlie respiration of air, with the addi- 

 tion of branchial lamellce (gills), for the respiration also of water. 



The Pubnobranchiate, or lung-gillcd, inoperculated Cephals are 

 possessed of a compound system of respiration, part lung, part 

 gill, by which they are enabled to breathe both air and water. 



