Crenaxula. mollusc a. PERNADyE. 391 



2. G ? acuta. — Ovate lanceolate, oblique, narrow, depressed, slightly cur- 

 ved ; anterior extremity acute ; teeth in the hinge variously disposed.^ 

 Sower. Min. Conch, t. dk. f. 5. — In Calcareous Sandstone., at CoUyweston. 



3. G. aviculoides. — Obliquely ovato-lanceolate, curved ; both extremities 

 pointed ; hinge-line nearly half the length of the shell ; hinge-teeth few — 

 Sower. Min. Conch, t. Ixi. and t. Dlxvi.— In Gh-een Sand and Oolite. 



Gen. CRENATULA. — Shell subequivalve, depressed; hinge 

 with numerous pits, without teeth for the reception of the 

 ligament. 



1. C. vent^icosa.— Ovate, elongated, ventricoso-carinated ; posterior side 

 impressed ; beaks pointed — Sower. Min. Conch, t. ccccxliii ? 



2. C. Listeri.—List. Conch, t. cccclxvii. f, 34-6 Park. Org. Rem. iii. 220. 



t. XV. f. 5 — Upper Oolite. 



3. Cproducta — Park. Org. Rem. iii. 221. t. xv. f. 6, 7.—" In a Marl-pit 

 near Shefford, in Bedfordshire." 



Gen. INOCERAMUS. — Shell inequilateral, irregular ; hinge 

 a marginal, subcylindrical, transversely sulcated callus, sup- 

 porting a ligament ; beaks conspicuous at one end of the 

 hinge. 



1. I. Cuvieri — Obovate, curved, convex, with transverse, distant, obtuse 



waves ; posterior side concave, with a small lobe near the beak Sower. 



Linn. Trans, xiii. 457 — Mant. Suss. 213. t. xxvii. f 4. t. xxviii. f. 1-4 — Ca- 



tillus Cuvieri, Cuvier, Oss. Foss. ii. 251. t. iv. f. 10 Sower. Min. Conch. 



t. ccccxli. f. 1. — In Chalky 



2. I. BrongniartL—Ohlong, gibbose, with large transverse undulations ; 

 anterior side angular, lobed ; posterior side flat, truncated and smooth ; beaks 



small, curved, and pointed — Mant. Suss. 214. t. xxvii. f. 8 Sower. Min. 



Conch, t. ccccxli. f. 2, 3 — In Chalk. 



3. I. mytiloides. — Equivalved, elongated, depressed, with slight irregular 

 waves ; convex and obtuse towards the beaks ; hinge-line oblique ; anterior 

 side produced ; beaks short — Mani. Suss. 215. t. xxviii. f 2.^Sower. Min. 

 Conch, t. ccccxiii. — In Chalk. 



4. I. cordiformis — Equivalved, heart-shaped, transversely and interrupted- 

 ly waved ; beaks large, incurved ; anterior side angular Sower. Min. Conch. 



t. ccccxl. — In Chalk. 



5. I. concentricus — Unequivalved, ovate, one of the beaks much produced, 

 incurved — {Park. Geol. Trans, v. 58. t. i. f i.)— Sower. Min. Conch, t. cccv. 

 — In Chalk Marl. 



6. I. sulcatus — Unequivalved, oblong, witii prominent beaks, and about 

 nine large longitudinal plaits ; beak of one valve, incurved, acute.— (Par*'. 

 Geol. Trans, v. 59. t. i. f. b.)— Sower. Min. Conch, t. cccvi.— In Chalk Marl. 



7- I. Lamarkii — Valves equal, very convex, with a few obscure lono^itudi- 

 nal undulations, and distant transverse ridges; surface covered with nume- 

 rous concentric striae ; posterior slope subdepressed ; anterior side lobaie, ex- 

 panded; hinge nearly transverse— {Park. Geol. Trans, v. 55.) — Mant. 

 Suss. 214. t. xxvii. f. 1 — In Chalk, 



