70 MOLLUSCA FROM THE CRAG. 



1. Limopsis aurita, Brocchi. Tab. IX, fig. 2. 



Arca aurita. Broc. Conch. Foss. Subap., p. 485, t. xi, fig. 9, a — b, 1814. 

 Pectunculus auritus. Defr. Diet. Scien., t. xxxix, p. 224. 



— — Gold/. Pet. Germ., v. ii, p. 163, t. 126, fig. 14, a— b. 



— _ Phil. En. Moll. Sic., vol. i, p. 63 ; vol. ii. p. 45. 



— — Risso. Hist. Nat. des Princip.Prod.de l'Europ., t. iv, p. 318, 1826, 



— suBLiEViGATUS. 5. Wood. Catalogue, 1840. 



— — Morris. Cat. Brit. Foss., p. 97, 1843. 

 Limopsis aurita. Sassi. Giorn. Ligust. (ex. Brown), 1827. 



— — Bronn. Leth. Geo., vol. ii, p. 935, t. 39, fig. 7, a— b, 1838 



— — Sismonda. Syn. Meth. Ped. Foss., p. 15, 1847. 



Trigonoccelia subl^vigata. Nyst. et West. Nouv. Rech. Coq. Foss. d'Anv., p. 12, pi. 2, 



fig. 15, 1839. 

 _ _ Nyst. Coq. Foss. de Belg., p. 244, pi. 26, fig. 2, a— b, 1844. 



Spec. Char. Testa obliqud, rotundato-ovatd, incequilaterd, sublavigatd, auriculatd ; 

 exilissime striata, et tenuissime decussatd; car dine arcuata, dentibus 10 — 18; margine 

 integer rime-) acuto. 



Shell oblique, rounded ovate, inequilateral, nearly smooth, and glossy, with small 

 auricles ; externally ornamented with very fine striae, crossed by distinct lines of 

 growth ; hinge line curved, with about 10 to 18 teeth ; margin sharp and smooth. 

 Longest diameter, \ an inch. 

 Locality, Cor. Crag, Gedgrave. 



This species has recently been found in abundance in one locality of the Coralline 

 Crag, but it appears restricted to that spot, it may possibly have lived on into the Red 

 Crag period, as my cabinet contains one specimen from that Formation, which however 

 is much water worn. 



It is subject to a good deal of variation in its outward form, but is always 

 more or less obliquely oval, generally becoming especially so in the older speci- 

 mens, while in some young shells the valves are nearly equilateral. The hinge is 

 composed of a row of denticles, varying from ten to sixteen, those on the shorter or 

 rounded side being the greater number, amounting to about nine, the outermost are 

 angular and somewhat distant, while the inner ones are close set and vertical ; on the 

 other side they are fewer, not exceeding seven, sometimes not more than four, these 

 are distant, much inclined, and nearly parallel to the hinge line, furthermore they are 

 often rough and crenulated upon their edges. The exterior of the shell is smooth and 

 even glossy when perfect, with faint but distinct radiating striae and visible lines of 

 growth, and the hinge line projects a little beyond the otherwise oval contour of the 

 shell, giving it the appearance of auricles, hence its name ; the inner margin is 

 flattened, smooth, and perfectly free from crenulations, and the impressions by the 

 adductors deeply seated ; that on the shorter side small and ovate placed near the 

 hinge, the other is larger and more distant ; the fossette for the cartilage diverges from 

 the umbo at an angle of about 90°. 



