BIVALVIA. 251 



Animal oblong, with very elongated siphonal tubes united almost to their extre- 

 mities ; orifices fimbriated. Mantle open in front for the emission of a foot of consider- 

 able size. 



The true position of this genus (or what is called its family connexions) is still a 

 subject of much diversity of opinion, some placing it near to Mtja, while others claim 

 for it a close aflfinity to Mactra. 



Few species of this genus are at present known in the recent state, and as fossils 

 they have been recorded in the Older Secondary Formations. The true generic 

 position of the latter is doubtful. In the Older Tertiaries it does not appear to have 

 been found, but the middle and newer Formations contain about nine or ten species. 



LuTRARiA ELLiPTiCA, Lumcirck. Tab. XXIV, fig. 1, a, b. 



Mactra lutraeia. Linn. Syst. Nat., ed. 12, p. 1126, No. 101, 1767. 



— — Brocchi. Conch. Foss. Subap., p. 536, 1814. 



LuTEARiA ELLIPTICA. Lamk. Hist, des An. s. Vert., torn, v, p. 468, No. 2, 1818. 



— — ? Basterot. Foss. de Bord., p. 94, 1825. 



— — Phil. Enum. Moll. Sic, vol. i, p. 9; vol. ii, p. 7. 



— — Desk. E.\p. Sci. Alger. Moll., pis. 33, 35, 36. 



— — Sismonda. Syn. Method. An. Inv. Fed. Foss., p. 23, 1847. 



— — Forb. and Hani. Hist. Brit. Moll., vol. i, p. 270, pi. 12. 



— — Nyst. Couch. Foss. de Belg., p. 75, 1844. 



— — ? Gratel. Cat. Zool. de Terr. Tert. de la Gironde, p. 76, 1838. 



— VULGARIS. Flem. Brit. An., p. 464, 1828. 



Lister. Hist- Conch. Lib., 1 1 1, fig. 259. 



Spec. Char. Testa ovato-ohlongd vel ellipticd, inceqiiilaterali, leeviusculd, antice suhangu- 

 lata, utrinque Jiiante ; sinu palliari prof undo. 



Shell ovately oblong or elliptical, inequilateral, somewhat smooth ; anterior side the 

 shorter, and slightly angulated ; gaping at both extremities ; pallial sinus deep. 



Letiffth, 5^ inches. Ileigld, 3 inches, nearly. 



Locality. Cor. Crag, Sudbourn and Ramsholt. 

 Red Crag, Sutton. 

 Clyde Beds, and Irish and Lancashire Drift Beds. (Forbes.) 



Recent, Mediterranean, Britain. 



This fine, handsome shell is, I believe, not very rare at Sudbourn, though specimens 

 of it are difficult to obtain. My cabinet contains one individual, with the two valves 

 united, which I found at Ramsholt. There is a slight difference in our fossil, varying 

 somewhat in its outline, more especially on the anterior or shorter side. In the recent 

 shell, the dorsal portion is there more convex or rounded ; but in the Crag specimen, 

 this part is nearly straight, giving an angular form to that side ; this difference, how- 

 ever, does not appear sufficient to affect the specific assignment. Each valve has a 



