114 NAYADES. 



iiiuch of its value. Other pearls, from the same places, have 

 sold for from £4. 10s. to £10. One at the last named price 

 was bought by Lady Glenlealy, who had it placed in a necklace, 

 and refused £80. offered for it by the Duchess of Ormond. We 

 are told by Camden, that Sir John Hawkins had a patent for 

 fishing pearls in the river Irt, Cumberland. There was also a 

 great fishery for pearls in the river Tay, Scotland, which ex- 

 tended from Perth to Loch Tay; and, it is said, the pearls sent 

 from thence to London, from the year 1761 to 1764, were 

 worth £10,000. sterling. It is not uncommon at the present 

 time to find pearls in the Teith and Tay, worth from £1. to 

 £2. each. 



Varieti/ 2. RoissYi, pi. XXII, f. 2, 3, and pi. XXI, f. 12. 



Unio Roissyi, Michaud, Conipl., p. 112, pi, 16, f. 28; 

 Proceedings Brit. Assoc, for 1838; Unio margaritifer, Iloss- 

 massler, I, pi. 4, f. 74 ; Forbes, Mai. Mon,, p. 44 ; Fleming, 

 p. 417; Thompson, Ann. and Mag. Nat. Hist., VI, p. 56; 

 Alasmodon Roissyi, Brown, Illust. Conch., p. 83, pi. 32, f. 13, 

 14, 15, and pi. 30,* f. 4. 



This variety differs from the common form in the following 

 particulars. The shell is much longer, in proportion to its 

 breadth ; it is more uniformly ovate, the teeth somewhat more 

 elevated; the exterior covered with very fine, transverse striae, 

 the epidermis blacker, and general surface more smooth ; the 

 hinge and basal lines less arcuated, interior more of a reddish- 

 blush, or flesh-colour, and the shell considerably thinner than in 

 the ordinary form ; the muscular impressions are smaller, and 

 less deep; the punctures are situate nearer the umbones, are 

 elongated, and not deeply sunk, being more lacrymose in their 

 appearance. 



Fig. 12, pi. XXI, external view of the teeth. 



This form inhabits the Teith, at Callander, Perthshire. 

 Forbes has found this elegant variety in the Black river, near 

 Kirk Bradden Church, and at Castleton, Isle of Man, where it 

 is common. He says " it was formerly much sought after by 

 the inhabitants for the sake of the pearls, which it not unfre- 

 quently contains." Mr. Thompson, on whose authority we give 

 this variety, says it is common to several localities in Ireland, 

 but does not particularize any of them. In the Teith, this form 

 attains a much larger size tjian in the Isle of Man. 



