BIVALVIA. 93 



I have seen but one specimen of this species from the Red Crag, which was found 

 by myself nearly twenty years since, and I presume it, therefore, to be rare in that 

 Deposit ; one specimen also from the Cabinet of Mr. Leckenby, found at Bridlington, 

 appears to belong to the same species, and they are both assigned to the recent 

 British one, and to the more ventricose or less transverse variety : specimens of the 

 recent shell, corresponding in every respect with our Crag fossil, have been obtained 

 by myself on the shore at low water on the Coast of Suffolk, and I have no hesitation 

 in pronouncing upon their identity. 



5. Leda pernula, Miiller. Tab. X. fig. 13, a — c. 



Arca pernula. Miill. Besch. Berl. Naturf. Fr., iv, 57, 1779, fide Loven. 



— Martini. Chem. Conch. Cab., t. vii, t. 206, fig. 550, 1784. 



— rostrata. Gmel., fide Lov6n. 



— _ W. Wood. Ind. Test., p. 47, pi. 10, fig. 43, 1825. 



— fluviatilis. Schfot. Flusc, p. 187, pi. 9, fig. 2, fide Desk. 

 Nucula fluviatilis. G. Sowerby, Genera No. 17, fig. 3. 



— oblonga. Brown. Illust. Conch. Gr. Brit., pi. 25, fig. 17, 1827. 



— rostrata. G. Sowerby. Conch. Illust., fig. 12. 



— — Desk. 2d ed. Lam., t. vi, p. 504, 1835. 



— Jacksoni? Gould. Inv. Massach., p. 102, fig. 65, 1841. 



— — Bekay. Nat. Hist. New York Zool., p. 181, pi. 12, fig. 213, 1843. 



— tenuisulcata. Couth. Bost. Journ. Nat. Hist., vol. ii, p. 64, pi. 3, fig. 8, 1839. 

 Leda rostrata. Forbes. Mem. Geol. Surv., p. 420, 1846. 



— — Schum. Essai, &c, p. 173, pi. 19, fig. 4, a — b, 1817. 



— pernula. Loven. Ind. Moll. Scand., p. 34, 1846. 



Spec. Char. Testa transversa elongatd, antice rotundatd, postice duplo longiori, in 

 rostrum obtusum attenuatd, concentrice striata. 



Shell transverse, elongate, anterior side rounded, posterior twice the length and 

 attenuated, terminating in an obtuse beak, concentrically striated. 



Longest diameter, -|ths of an inch. 



Locality. Mam. Crag, Bridlington. 

 Clyde Beds. 



One specimen (fig. 13, c) belonging to Mr. Bean, found at Bridlington, and 

 obligingly lent to me by that gentleman for the purpose of description, appears to 

 be somewhat different from the preceding, it corresponds with the recent form found 

 in the Boreal Seas of Europe, and which is most probably also a native of the 

 Northern Coast of America. Our fossil is not in good condition, being compressed 

 and slightly broken, and its natural form in consequence somewhat distorted, but it is 

 sufficiently perfect to permit of a presumed evidence of identity with the recent species. 

 It is more inequilateral than the preceding species, larger, and with finer concentric 

 striae, corresponding with the figure and description of N. tenuisulcata, Couthouy, and 

 of which, probably, N. Jacksoni, Gould, is only a variety. Fig. 13, a, b, is the repre- 

 sentation of a specimen from the Clyde Beds, given to me by Jas. Smith, Esq., of 



