2 REPORT 1865. 



individual of Aplysia performs the functions of one sex only, while each snail 

 is at the time of sexual union both male and female. 



The tide ebbs far on the coasts of the Channel Isles, especially during the 

 equinoxes ; at Guernsey the reflux extends about 30 feet, and at Jersey up- 

 wards of 40 feet. This is very different from what takes place in the Medi- 

 terranean, and it occasions a remarkable variation of habitat in many species. 

 Psammohia costulata lives at Herm in the sand which is laid bare at low 

 water, but in Shetland it occurs at a depth of between 80 and 90 fathoms. 

 Hence we may infer that the depth of water cannot always be safely pre- 

 dicated from a cursory examination of shells either in a recent or fossil state. 

 Their comparative solidity and size afford better criteria *. 



A collection of the shells obtained on the present occasion has been placed 

 in the British Museum. 



We were indebted to Mr. Lukis, Mr. Gallienne, Mr. Macculloch, Mr. Le 

 Lievre and Mr. Cooper, of Guernsey, and to Mr. Piquet and Mr. Rose of 

 Jersey, for much assistance and pleasant companionship. From the first- 

 named of these gentlemen I received Purpura hcemastoma, from the second 

 Emarginula cancellata, and from the third Triton (or Murex) cutaceus, all of 

 which had been taken alive at Guernsey and Herm. There cannot be the 

 slightest reason to doubt that Triton nodiferus, as well as T. cutaceus, inhabit 

 this part of our seas. MM. Cailliaud and Tasle have recorded the latter 

 species, and M. Cailliaud the former, as natives of the coast of Brittany. 



Off Jersey were dredged a few worn specimens of Cerithium vulgatum, a 

 species which does not seem to have been observed in a living state anywhere 

 on the shores of the North Atlantic. It is common throughout the Medi- 

 terranean and Adriatic. M. Cailliaud has included it in his list of shells from 

 the Loire-Inferieure, but only in a dead and rolled condition. From careful 

 inquiries which I made at Jersey, I am enabled to state with some degree 

 of certainty that no ballast containing shells has ever been brought there. 

 I should be disposed to attribute the presence of C. vulgatum (as a semi- 

 fossil shell) on the coasts of Jersey and Lower Brittany to an ancient sub- 

 mergence of the land, at a period probably anterior to that when submarine 

 forests and peat-beds were formed on the shores of the north of Europe, and 

 when the bays of St. Aubin and St. Michel were produced. Fossil shells, of 

 Eocene species, were likewise met with ; and they will be noticed in the 

 Geological Section of this Meeting. 



The following Tables may be useful to show which species are apparently 

 restricted to the more southern limits of Great Britain. 



I. Species found in the Channel Isles but not in Shetland : — 



Argiope decollata. 



capsula. 



Mytilus barbatus. 



Adriaticus. 



Modiolaria costulata. 

 Crenella rhombea. 

 Area lactea. 

 Galeomma Turtoni. 

 Lepton squamosum. 



sulcatulum. 



Loripes lacteus. 

 Diplodonta rotundata. 

 Cardium aculeatum. 



Cardium tuberculatum. 



papillosum. 



Tapes aureus. 

 Gastrana fragilis. 

 Psammobia vespertina. 

 Donax vittatus. 



politus. 



Amplndesma castaneum. 

 Mactra glanca. 

 Lutraria oblonga. 

 Scrobicularia tenuis. 

 Solen vagina, 

 Mya Binghami. 



* See ' British Conchology,' vol. iii. p. 27. 



