Terebratula. MOLLUSCA. ACEPHALA. 371 



convex ; front defined by two angles, or emarginate ; edge becoming blunt 

 by age Sower. Min. Conch, t. ccccxxxv. f. 5 — Upper Oolite. 



27- T. globata. — Subglobose ; front elevated with two obtuse folds, and 

 slightly produced ; surface often minutely punctated — Sower. Min. Conch. 

 t< ccccxxxvi. f. 1. — Upper Oolite. 



2!J. T. perovalis.— Ovate, convex, with two elevated sinuses at the front, 

 which is depressed between them ; beak incurved — Sower. Min. Conch, t. 

 ccccxxxvi. f. 2, S — Under Oolite. 



29. T. maxillata — Subquadrangular, convex ; two acute rising sinuses in 

 the front, and one obtuse sinus on each side ; three conspicuous furrows in 

 the upper, and two in the lower valve ; front rounded — Sower. Min. Conch, 

 t. ccccxxxvi. f. 4. — Upper Oolite. 



30. T. Sella Subquadrangular, convex ; front considerably elevated, nar- 

 row, emarginated when old ; sides depressed, slightly rounded — Sower. Min. 

 Conch, t. ccccxxxvii. f. 1. — Upper Oolite. 



31. T. obtusa. — Subovbicular, rather depressed ; front broad, elevated ; 

 edge obtuse Sower. Min. Conch, t. ccccxxxvii. f. 4.— From Cambridge. 



32. T. obesa Ovate, gibbose, front elevated considerably, with a slight 



broad sinus in the middle ; beaked valve regularly convex to the edge ; beak 

 incurved, short Sower. Min. Conch, t. ccccxxxviii. f. 1. — In Chalk. 



33. T. bucculenta.— Rather square, with rounded sides, convex ; front pro- 

 duced, truncated, very slightly elevated ; beak short —Sower. Min. Conch. 

 t. ccccxxxviii. f. 2. — In Green Sand. 



34. T. triquetra Suborbicular, with a produced incurved beak ; valves 



equally convex ; front slightly indented ; beak obtusely keel-shaped, with a 

 cai'ina on each side Sower. Min. Conch, t. ccccxlv. f. 1 — In Oolite. 



35. T. indentata Elliptical, smooth, more or less gibbose ; valves equally- 

 convex; front deeply notched; beak small, much incurved — Sower. Min. 

 Conch, t. ccccxlv. f. 2. — In Limestone at Banbury. 



36. T. Sacculus.— Obovate, gibbose, with a longitudinal groove along the 

 larger valve ; the smaller valve slightly grooved ; front emarginate — Anomia 

 kevis, Ure's Ruth. 313. t. xvi. f. 0.— A sacculus, Martin's Derb. t. xlvi. f. 1, 2. 

 — Ter. Sacc. Sower. Min. Conch, t. ccccxlvi. f. 1.— In Carboniferous Limestone. 



37- T. hastata Elliptical, subrhomboidal, rather depressed ; front trun- 

 cated and indented ; edges sharp — Soiver. Min. Conch, t. ccccxlvi. f. 2, 3. — 

 Greywacke Limestone, Cork. 



38. T. cornuta Short, convex, with blunt edges, four-lobed ; the two 



middle lobes produced ; the others very short — Sower. Min. Conch, ccccxlvi. 

 £ 4.— In Oolite. 



39. T. ambigua Subpentangular, gibbose, perforated valve with a broad 



mesial groove, with a mesial ridge, having a shallow central furrow enlarging 

 at the margin. — Spirifer ambiguus, Sower. Min. Conch, t. 376 — Carboniferous 

 Limestone. 



** Margin of the valves dovetailed. 



40. T. lateralis.— Oval, broader than long, gibbous ; middle of the front 

 much elevated, with three deep but short plaits ; sides with two plaits each, 

 much below the middle— Sower. Min. Conch, t. lxxxiii. f. 1.— In Carbonife- 

 rous Limestone. 



41. T. emmena.— Deltoid, gibbous, plaited; middle of the front elevated, 



A a 2 



