JACKSON : ON UNIO SINUATUS IN rHE BRITISH ISI.F.S. I43 



nicirgariti/era appears to be known in France as tlie var. elongata 

 Lam., and this name might very well be adopted in this country. 

 The var. arcnata Barnes, met with in North America, also appears 

 to be this form, but Lamarck's name has precedence over tliis. 



It will be necessary now to carefully examine all previous records 

 of the so-called var. sinuata to see if the shells possess lateral teeth 

 or not. As mentioned previously, I have already examined a large 

 number recorded as var. sinuata, and have noted the entire absence 

 of lateral teeth therein. These, therefore, have no relation with the 

 Lamarckian species, but belong to Margaritana margaritifera (L.). 



The Dumfries specimen is undoubtedly Unio siuuattis Lam., and 

 agrees in all its particulars with the descriptions and figures given by 

 Rossmassler,^ Moquin-Tandon,- and others. It is, however, the only 

 specimen I have as yet seen from this locality, and I should be glad, 

 therefore, to hear from other collectors who may have specimens from 

 there in their collections. I should also be glad if anyone possessing 

 British specimens of the Pearl Mussel would communicate with me 

 and send a list of what localities are represented, in order to complete 

 my paper on the species. 



A good opportunity presents itself here to call attention to the 

 paper I wrote, in conjunction with Mr. A. S. Kennard, on the occur- 

 rence of Unio viargaritifer in the Pleistocene strata of the Thames.^ 

 The shells referred to in this paper w^ere dredged at Mortlake,^ and 

 were recorded as the var. sitiuata Lam., but owing to the incrustation 

 of carbonate of lime, both inside and outside, the hinge-teeth were 

 not properly examined. Dr. Fritz Haas, of Frankfurt, to whom one 

 of the Thames shells was sent, has since kindly pointed out to us the 

 fact that the Thames mussel possesses lateral teeth, and is, therefore, 

 the Unio sinuatus Lam., and not Margaritana margaritifera (L.), as 

 given in our paper. '^ A careful examination of the specimens in our 

 hands confirms this fact. The Thames specimens, therefore, being 

 Unio sinuatus Lam. and not Margaritana margaritifera (L.), Dr. 

 R. F. Scharff's statement in his European Animals,® " that the Pearl 

 Mussel is absent from the South-east of England — the area so 

 characteristic of the Germanic species " — still holds good. 



1 Iconographie, 1836, i., p. 22, pi. 13, f. 195 ; and 1S54, iii., p. 38, pi. 70, f. 853, 853a. 



2 Hist. Nat. Moll, de France, 1855, p. 567, pi. 48, f. 1-3. 



3 Journ. of Conch., vol. xii., p. 321. 



4 Mr. Kennard tells me they have since been dredged at Barn Elms, E. Surrey. 



5 See also his paper on " Unio, Margaritana, etc., in the Thames Valley," Proc. Malac. 

 Soc, vol. ix., pt. ii., June, 1910, p. 106, in which this is discussed. 



6 London, 1907, p. 72. 



