BIVALVIA. 83 
surface can be examined and compared, the minute, crowded pattern upon fs sinistra, 
with the widely separated lines of granules upon JZ. decurtatum. 
Geological Positions and Localities. ‘The Cornbrash of Scarborough; in the col- 
lection of Mr. Leckenby. . In Switzerland M. Agassiz records it from the same geological 
position (calcaire roux-sableux) at Goldenthal, Soleure ; also in the Bernese Jura. 
Myacires mopica, Bean, sp. ‘Tab. XLII, figs. 1, 1 a. 
Mya mopica, Bean. Mag. Nat. Hist., 1839. 
Testa-ovato elongata subdepressa, umbonibus subdepressis antemedianis, margine antico 
producto, rotundo, postico oblique declivi subrecto, margine inferiore elliptico curvato, area 
ligamenti lanceolata lata, subdepressa, marginibus acutis, valvis lateribus concentrice delicate 
plicatis ; lineis radiantibus granulatis, subtillissimis dense instructis. 
Shell ovately elongated, rather depressed; umbones antero-mesial, rather depressed ; 
anterior margin produced, rounded; posterior margin more lengthened, nearly straight, 
sloping downwards obliquely, lower border curved elliptically ; the granulated test consists 
of extremely delicate, very densely arranged, radiating lines, visible only under a magnifier; 
the concentric plications are numerous and faintly traced, so that the surface is smooth; 
the valves are close-fitting, or have no perceptible aperture at either of the extremities. 
Length, 24 inches; height, 13 inch; diameter through both the valves, * inch. 
The general figure and aspect of this species renders it easy to distinguish from other 
examples of the genus. 
Geological Position and Locality. The Cornbrash of Gristhorpe Cliffs, in which it has 
occurred very rarely ; Mr. Leckenby’s collection. 
AnatTiIna (CerEomyYA) sIniaua, 47. ‘Tab. XXXV, fig. 15. 
SANGUINOLARIA UNDULATA, Phil. Geol. York., i, pl. 5, fig. 1, non Sow. 
Crrcomya sitiqua, 4g. Et. Crit. Myes., p. 148, tab. 11 a, figs. 9—13. 
— ANTICA, dg.? Ib., p- 147, tab. 11, figs. 16—18; tab. lla, 
figs. 14—16. 
Anatina Betiona, D’Orb. Prod., i, p. 336, 12 ét., No. 132. 
— wnpData, Id. Ib; > jp-13615) 13Het:, Nos 221, 
SANGUINOLARIA UNDULATA, Quenstedt. Der Jura, p. 508, t. 68, fig. 9. 
ANATINA UNDULATA, Leckenby. Proc. Geol. Soc., vol. xv, 1858. 
Testa transverse elongata inequilatera umbonibus subanticis parvis acutis, postice 
