198 Mr. Jeffreys on the Comparative Size of Marine Mollusca. 



pendently of my Mediterranean dredgings), enable me to sub- 

 stantiate the proposition which I ventured to enunciate in a 

 former Number of the 'Annals' (ser. 3. vol. ii. p. 120), that, "in 

 general, the size of specimens increases in a ratio inverse to their 

 northern, and converse to their southern, point of latitude." 



I will now consider, seriatim, all the instances adduced by 

 Mr. M 'Andrew, by which he seeks to disprove my proposition. 



1. Corbula nucleus. This species is very variable in respect 

 of size on the British coasts ; and Mr. M' Andrew may have 

 found a small variety upon the shores of North Drontheim. 



2. Trochus lineatus. Specimens which I have collected in 

 Wales and Donegal Bay considerably exceed in size Mr. M 'An- 

 drew's specimens from the north coast of Spain and Mogador. 



3. Astarte sulcata. Most variable in size on our own coasts, 

 and probably also in the northern localities indicated by Mr. 

 M'Andrew. 



4. Astarte triangular is. I believe I can match, in point 

 of size, specimens from North Britain with any which Mr. 

 M 'Andrew has from Gibraltar Bay. 



5. Crenella (Modiola) marmorata. The largest specimens I 

 ever saw were said to come from Greenland. 



6. Crenella rhombea. The size of some of my specimens from 

 Guernsey is fully equal to that of Mr. M' Andrew's largest speci- 

 men from the Canaries or Mediterranean. 



7. Nucula nucleus. * Mr. M 'Andrew's specimens from Finmark 

 appear to be a small variety, which also occurs on our own coasts. 



8. Nucula decussata. Mr. M'Andrew's specimens from the 

 south of Spain are not much more than half the size of my 

 Oban specimens. 



9. Cardium rusticum. Mr. M f Andrew had probably not seen 

 the very large examples from the south of Devon when he 

 stated that this species increased in size southward from the 

 British Channel. 



10. Cardium papillosum. This has only recently been dis- 

 covered to inhabit the British Isles; but a specimen in Dr. Lukis's 

 cabinet is quite as large as any that I have seen from the Medi- 

 terranean. 



11. Cardium pygmceum. Mr. M' Andrew's specimens from 

 Vigo Bay are not so large as some which the late Mr. Warren 

 sent me from the south of Ireland ; and I found specimens nearly 

 as large as the last at Falmouth. 



12. Venus verrucosa. British specimens are larger than any 

 which I have seen from more southern latitudes. 



13. Mactra stultorum. I suspect that the specimens men- 

 tioned by Mr. M 'Andrew belong to another species, probably to 

 the M. inflata of Bronn. 



