TRUNCATELLA. 381 
littorea of authors. These, though sent by post in moistened 
weed, which however was quite dry when received, on bemg 
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, 1 
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 Conovulus denticulatus 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 
Littorine, particularly L. neritoides, which are attached to 
rocks for long periods, perhaps durimg 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 Truncatelle 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 very 
‘rare and local. 
