TEFNCATELLA. 381 



littorea of authors. These, though sent by post in moistened 

 weed, which however was quite dry when received, on being 

 put into sea-water immediately deployed the organs. The 

 first has been described by the Rev. R. T. Lowe, many years 

 ago, in the 5th volume of the ' Zoological Journal/ p. 303 ; 

 and the R. littorea, by the learned authors of the ' British 

 Mollusca/ in the Appendix, vol. iv. p. 265 ; still, as my account 

 contains many new particulars, and notes a difference of 

 opinion in respect of the generic position of R. littorea, I 

 have thought it would be agreeable to some readers to have 

 a description of these rare creatures from a fresh though 

 inferior hand, especially as the present notes exhibit a 

 comparative view of both animals, which were examined for 

 two days in the same vase under very favourable circum- 

 stances. It is singular that these species, both undoubted 

 Pectinibranchiata, should inhabit at high water level, in com- 

 pany with Conovulm denticulatw and C. bidentatus, both 

 Pulmonifera, and are, as Mr. Thompson has informed me, 

 "decidedly amphibious," being often found far above that 

 limit ; but I apprehend not more so than many of the minuter 

 Littorince, particularly L. neritoides, which are attached to 

 rocks for long periods, perhaps during their whole existence, 

 above the highest tides and even beyond the reach of the 

 spray, living apparently on the floating saline moisture. It 

 would appear then that the two respiratory systems are in 

 respect of these animals on the limits of their respective 

 boundaries, and form the transitions from one to the other. 

 Both the Pectinibranchiates escaped from the water as quickly 

 or quicker than the Pulmonifera, but all the former, whether 

 littoral or from deep water, have the same propensity ; there- 

 fore this fact is of little value ; yet, when strictly confined, 

 the Truncatella continued lively for two days, whilst the 

 Conovuli became torpid in twelve hours: perhaps we may 

 conclude, that these littoral Pectinibranchiata and the sub- 

 littoral Pulmonifera are to a certain extent amphibious. All 

 these species were taken mixed together in an estuary at 

 Portland, by Mr. Thompson, who states that they are verv 

 rare and local. 



