38 SYRIAN MOLLUSCAN FOSSILS. 



LAMELLIBRANCHIATA. 



Corbula aligera, sp. nov. 



Plate IV, tigs. 6 a, b, c, d. 



Testa parva, triquetra, vncequHateraUs, clausa ; valvula dextra pernio major guam 

 sinistra; postice acuminata, valde angulaia; margo antieus insinuatus et infra rotun- 



datv.s : iimbones wdetnediani, supcme appressi et obtusi, involuti, antrorsum intorti: 

 superficies rugis sive varieibus concentricis irregularibus crassis induta : lunula infra 

 illimitata ; arm cardinalis perangusta, lanceoMa, tenuiter excavata. Carina acida 

 alata, ab umbonibus ad terminationem postero-inferiorem rede decurrens, aream pos- 

 liniHi subconcavam costuHs radiantibus instructam a laferibus dividit. 



Shell small, triangular, inequilateral, perfectly closed at the margins ; 

 right valve a little larger than the left, and tightly overlapping it ; pos- 

 teriorly acuminate, strongly angled ; anterior margin sinuated above and 

 rounded below : umbones a little in front of the middle point of the shell, 

 obtuse above as if pressed downward, involute and bent forward: surface 

 covered with thick, irregular concentric plaits, or varices : lunule undefined 

 below ; hinge area very narrow, lanceolate, slightly excavated. A sharp, 

 wing-like keel, running straight from the beaks to the postero-inferior ex- 

 tremity, divides from the lateral surface the subconcave hinder area, which 

 is marked with radial riblets. 



Three specimens. Length, 9^ mm. to 10^ mm. ; height, G mm. to 7 mm.; 

 thickness, inside of keels, 1 mm. to 5 mm. 



The concentric plaits are much narrower than the intervals which sepa- 

 rate them. They stop short upon the thin and elevated keel, and are wholly 

 distinct from the more numerous radiating riblets which adorn the nearly 

 flat posterior area. In these unusual features, the species approaches C. Yal- 

 densis Hebert and Renevier " du Terrain Nummulitique superieur." (Fossiles 

 dii Terrain Nummulitique supe'rieur des Environs de Gap. des Diablerets, et 

 de quelques Locality de la Savoie. Grenoble, L854, p. 50, PI. i, fig. 11.) 

 Coll. Bird. 



Locality ami Position. — From arenaceous marl, probably Turonian and 

 from the vicinity of Abeih. 



