112 CRETACEOUS LAMELLIBRANCHIA. 



Remarks. — Since the name Omalioides has been used in stratigraphical lists, 1 it 

 seems desirable to retain it, although its construction is not in accordance with the 

 recommendations of the International Congress of Zoology. 



Distribution. — Gault (zones vii, x, and xi) of Folkestone. 



Astarte Formosa, Sowerby, 183G. Plate XV, figs. 8-13. 



1836. Astarte Formosa, J. de 0. Sowerby. Trans. Geol. Soc, ser. 2, vol. iv., pp. 



239, 341, pi. xvi, fig. 16. 

 1842. — — F. Bdmer. De Astartaruin Genere, p. 21. 



1850. A. d'Orbigny. Prodr. de Pal., vol. ii, p. 160. 



1854. — /. Morris. Cat. Brit. Foss., ed. 2, p. 186. 



1871. — F. Stoliczka. Palseont. Indica, Cret. Fauna S. India, vol. 



iii, p. 285 (? Gouldia). 



Non 1842. — H. B. Oeinitz. Char. d. Schicht. u. Petref. des s'achs.- 



bohm. Kreidegeb., pt. 3, p. 76, pi. xxi, 

 fig. 19 (see Geinitz, Elbthalgeb. i, p. 

 227). 

 - 1844. A. d'Orbigny. Pal. Fran?. Terr. Cret., vol. iii, p. 65, pi. 



cclxii, figs. 10 — 12 (A. subformosa, 

 d'Orb., 1850). 



Description. — Shell small, rather convex, sub-triangular, moderately inequilateral. 

 Antero-dorsal margin slightly concave. Anterior and ventral margins forming a 

 regular curve. Posterior margin less curved, often truncated, and forming an 

 obtuse angle with the long and slightly convex postero-dorsal margin. Umbones 

 pointed. Lunule large, ovate, depressed, smooth, with a sharp border. Escutcheon 

 long, lanceolate, depressed, smooth, with a sharp border. Margins of valves smooth. 



Ornamentation consists of strong concentric ribs with sharp summits, separated 

 by broad concave interspaces. The ribs end abruptly at the margins of the lunule 

 and escutcheon. On the ribs and interspaces fine concentric ridges may be seen. 



Measurements : 



(1) (2) (3) (4) (5) (G) 



Length . 5*0 . 475 . 4>5 . 4-0 . 3-25 . 3'0 mm. 

 Height . 4-5 . 4'5 . 4-0 . 375 . 3'0 . 2-5 „ 



(1—6) Blackdowii. 



. [ijiuities. — A.formosa is smaller and has more numerous ribs than .1. subformosa, 

 1 Price, 'The Gault ' (1879), p. 58; Jukes-Browne, 'Cret. Rocks of Britain,' vol. i (I960), p. 465. 



