208 MOLLUSCA FROM THE CRAG. 



The recent species Necera hjalina, Hinds, appears to be more nearly connected with 

 Thetis, having an external ligament on a thin and semi-transparent shell, differing 

 thereby from our fossil, which is a thick one. The two shells figured by Messrs. 

 Reeves and Adams in the ' Zoology of the Voyage of the Samarang/ may perhaps 

 belong to Thetis, but the position of the ligament is not stated, and the shells are 

 described as being quite smooth and thin. 



The Cretaceous fossils of India and Westphalia, assigned to this genus, have not 

 as yet had their characters sufficiently well determined. 



1. Poromya granulata, Nyst and Westendorp . Tab. XXX, fig. 5, a—f. 



Corbxjla gkanulata. Nyst and West. Nouv. Reck. Coq. Foss. d'Anv., p. 6, No. 10, 



pi. 3, fig. 3, 1839. 



— ? — Nyst. Coq. Foss. de Belg., p. 71, pi. 2, fig. 6, 1844. 



— ? — Jeffreys. An. and Mag. Nat. Hist., vol. xix, p. 314 ; and vol. xx, 



p. 19. 

 Poromya anatinoides. Forbes. vEgean. Invert. Brit. Assoc. Report, p. 191, 1843. 



— granulata. Forb. and Hani. Hist, of Brit. Moll., p. 204, pi. 9, figs. 4 — 6, 



1848 ; and Animal, pi. w, fig. 2, 1853. 

 Embea Korenii. LovSn. Ind. Moll. Scand., p. 46, 1846. 



Spec. Char. Testa ovatd, ventricosd, subcequilaterali ; antice rotundatd, postice trun- 

 catd, et obtuse angulatd; acideis minutissimiss criberrimis aspera; umbonibus prominenti- 

 bus ; dente unico obtuso. 



Shell ovate, ventricose, slightly inequilateral ; anterior side rounded, posterior 

 truncated, with an obtuse keel or ridge retreally from the umbo to the ventral 

 margin ; beaks prominent ; one obtuse tooth. 



Length, ^ inch. Height, •§ inch. 



Locality. Cor. Crag, Ramsholt, Sutton, and Gedgrave. 



Recent, iEgean, British, and Scandinavian Seas. 



About a dozen disconnected valves have been obtained by myself, several of them 

 sufficiently perfect for fair comparison, and I have considered them as identical with 

 the Belgian fossil and the .ZEgean and Scandinavian shell. 



The hinge of the right valve is furnished with one large obtuse tooth, situated 

 immediately beneath the umbo, and in the left there is a corresponding cavity between 

 two small prominences for its reception ; behind these, and within the dorsal margin, 

 is a depression wherein, I presume, the ligament was placed : this cavity is divided by 

 a small ridge, which appears to have separated the cartilage from the ligament, and 

 the latter probably was visible externally when the valves were closed : there is a 

 small depression on the siphonal side at the dorsal edge, what may perhaps be 

 called the corslet, produced probably by the opening of the valves ; but there is no 

 ridge or fulcrum for the support of an external ligament. The impressions by the 



