246 MOLLUSCA FROM THE CRAG. 



Mactra vulgaris. Chemn. Conch. Cab., vol. vi, p. 230, pi. 23, fig. 229. 

 Trigonella zonaria. Da Costa. Brit. Zool., p. 197, pi. 15, fig. 1, 1778. 



— gallina. Id. Brit. Zool., p. 199, pi. 14, fig. 6. 



Spisula solida. Gray. Mag. Nat. Hist., 1837, p. 374. 



Spec. Char. Testa ovato-trigonali, subaquilaterali, crassd, laviusculd; dentibus 

 lateralibus perpendiculariter striatis. 



Shell triangularly ovate, slightly inequilateral, thick, nearly smooth ; lateral teeth 

 perpendicularly striated. 



Length, 1 inch. Height, -| inch. 



Locality. Red Crag, Sutton. 



Mam. Crag, Bramerton. 



Clyde Beds. Recent, Mediterranean and British Seas. 



As far as I can ascertain the history of this species, it is of comparatively modern 

 origin, although by some mistake it was quoted in my ' Catalogue ' as from the Older 

 or Coralline Crag, from which deposit I certainly have not a well-determined specimen, 

 and those from the succeeding or Red Crag Period are somewhat doubtful. 



I have one characteristic specimen from Bramerton, corresponding precisely with 

 the common living shell, but it does not appear to have been abundant even there, as 

 it is not enumerated among the Norfolk Shells by Woodward. 



In the recent state, it is generally a littoral species, living buried in the sand, but 

 has been found in water as deep as thirty- five fathoms {M' Andrew). It is an estuary 

 species at the present day. 



8. Mactra ovalis, /. Soiverby. Tab. XXIII, fig. 1, a — d. 



Mactra ovalis. J. Sow. (not Gould.) Min. Conch., t. 160, fig. 5, 1817. 



— dubia. Id. Min. Conch., t. 160, figs. 2, 3, 4. 



— elliptica. Brown. Illust. Conch. Gt. Brit., pi. 15, fig. 6, 1827. 



— — Lov6n. Ind. Moll. Scand., p. 45, 1846. 



Forb. and Hani. Hist. Brit. Moll., vol. i, p. 356, pi. 22, fig. 3. 



— solida. Don. Brit. Shells, t. 61, small figure. 



— congesta? Conrad. Foss. of the Med. Tert., p. 27, pi. 15, fig. 2, 1838. 



— striata. Nyst. Coq. Foss. de Belg., p. 80, pi. 4, fig. 1 a, 1844. 

 Spisula elliptica. Gray. List Brit. Moll., p. 32, 1851. 



Spec. Char. Testa elliptica vel ovato-angulatd, subaquilateraii, laevigata, vel tenuis- 



striatd, liuuidiusculd ; dentibus lateralibus rugosis ; margine ventrali arcuato. 

 Shell elliptical or angularly ovate, nearly equilateral ; smooth or very finely striated 

 transversely ; slightly tumid ; lateral teeth rough or striated ; ventral margin curved. 

 Length, 2 inches. Height, 1^ inch. 



