106 CRETACEOUS LAMELLIBRANCHIA. 



Astarte, sp. nov., one is in the Sedgwick Museum (fig. 9 a), the other in Mr. J. F. 

 Walker's collection (fig. 9 6). 



Distribution. — Lower Greensand of Upware. 



Astarte senecta, sp. nov. [ex Bean MS.] Plate XIV, figs. 13-20. 



1889. Astarte senecta [Bean MS.] G. W. Lamplugh. Quart. Journ. Geol. Soc, 



vol. xlv, p. 616. 



Description. — Shell subtriangular, or approaching subquadrangular, sometimes 

 rounded, rather compressed, usually very inequilateral; height usually a little 

 greater than length. Anterior margin rounded, ventral margin curving slightly 

 and often forming a rounded angle with the posterior margin, which is slightly 

 curved and usually makes an obtuse angle with the postero-dorsal margin. 

 Umbones small, curving forwards. Lunule ovate, deep, with a sharp border. 

 Escutcheon narrow, deep, with a sharp border. 



Ornamentation consists of strong concentric ribs, with sharp summits, separated 

 by broad furrows, on both of which are numerous small ribs. The ribs bend 

 sharply in passing on to the postero-dorsal part of the valve, and cut the postero- 

 dorsal margin obliquely. Margins of valves strongly crenulated. 



Measurements : 



(i) (2) (3) (4) 



Length . 23 22 21 19 

 Height . 21-5 20 19 17 



(1-5) Speeton Clay, Speeton. 

 (6-11) Claxby Ironstone, Benniwortli Haven. 



Affinities. — Astarte veneris, Eichwald, 1 is similar to this species, but has a 

 deeper and larger lunule, more prominent umbones, less compressed valves, and 

 more slender ribs. Specimens of A. veneris from the ' Volgian ' of Moscow are 

 in Mr. Lamplugh' s collection. 



Remarks. — This species has been known to collectors for a long time, and has 

 appeared in lists of fossils under the name Astarte senecta, Bean MS., but has not 

 hitherto been described and figured. 



The specimens from the Claxby Ironstone are, as a rule, more rounded in 

 outline than those from Speeton, and their ornamentation is not so well preserved 

 on account of the difficulty of separating the shells from the hard matrix in which 

 they are found. 



1 D'Orbigny, in Murchison, de Verneuil, and de Keyserling, ' Grcol. Euss. d'Europe,' vol. ii (1845), 

 p. 456, pi. xxxviii, figs. 21, 22. 



(5) 



(6) 



(V) 



(8) 



(9) 



(10) 



(ii) 



13 



26 



25 



25 



23 



23 



21 mm 



11 



24 



22-5 



22 



23 



22 



21 „ 



