Mr. R. M'Andrew on the Comparative Size of Mollusca. 313 



has not yet been made between the largest in Mr. Jeffreys's 

 possession and in mine. 



7. Nucula nucleus. INIy specimens from Norway are of the 

 ordinary British form, and are no more a small variety than are 

 those from Spain and Portugal. 



8. Nucula deciissata. I cannot but think that Mr. Jeffreys 

 must be labouring under a mistake; otherwise his specimen 

 from Oban must be very extraordinary, and quite exceptional in 

 its dimensions. Of the few specimens I obtained off Malaga, 

 the largest measures about seven-eighths of an inch in its greatest 

 diameter; the largest of many specimens obtained off Oban at 

 various times is smaller by about an eighth of an inch. 



9. Cardium rusticum. All the British specimens I have seen 

 of this species are from South Devon. Upon one occasion, after 

 an equinoctial spring-tide and gale of wind, I saw such quanti- 

 ties of this species, in company with C. aculeatum, thrown upon 

 the shore of Torbay in a living state, that they might have been 

 collected by the bushel. The specimens of both species, but 

 more particularly C rusticum, are much smaller there than at 

 Gibraltar and in the West ]Mediterranean. 



10. Cardium papillosum I have not met with north of Vigo, 

 where the specimens are smaller than in the Mediterranean : 

 .size of latter five-eighths of an inch, or rather more. I should 

 like to know the exact dimension of Dr. Lukis's specimen — if, 

 indeed, the species is identical ; though, in any case, a single 

 specimen could not give much weight to an argument. 



11. Cardium prjymaium I have taken in the south of Ireland 

 (Cork Harbour), as well as various British localities, but in none 

 so large as the average of those in A^igo Bay. It should be 

 borne in mind that the question is regarding the size generally 

 attained by species in the different latitudes. 



1.2. Venus vei-rucosa. Mr. Jeffreys would appear to have seen 

 only small specimens from southern localities. My British 

 specimens were from Pwllheli, where, as the most northern limit 

 of the species, according to Mr. Jcffreys's theory, the largest 

 specimens ought to have been found. The Rev. ]\Ir. Norman, 

 with a view to improve my specimens, very kindly sent me 

 others, which I may presume to be at least equal to the average 

 in size ; but these, as well as all the other British specimens I 

 have seen, arc decidedly smaller than the average of adult speci- 

 mens from Gibraltar, and of those which arc taken abundantly 

 from Minorca to be sold as food in the market of Algiers. 



13. Mactra stultorum. It is very possible that Mr. Jeffreys 

 may be correct in his suspicion that the specimens alhuled to 

 by me may belong to M. injlata of Bronn, though I much doubt 

 their being specifically distinct. 



Ann. a^ Mag. N, Hist. Ser. 3. Vol.\. 21 



