PUCATULA. 



CONCHIFERA. 



151 



straight and obtuse ; auricles small, the anterior one longest, 

 situated in a large, broad, deep furrow ; surface smooth, with 

 obscure longitudinal divergent stri;c ; and crossed by a few 

 hollow lines of growth. 



Inferior Oolite, Glaizdale and Cotswold, and the Liae, 

 Weston and Lyme Regis. 



2. Plaoiostoma spiNOsmi. — The Spinous Plagiostoraa, 

 pi. LXVL* tig. 4. 



P. spinosa. Sowerby, I. p. 177, pi. 78. Spondylus, Gold- 

 fuss, pi. 105, fig. 5. 



Obovatc ; umbones nearly central and rather blunt ; sides 

 nearly equal, and not much arched ; one Talve flat and the 

 other more inflated ; surface with numerous flat ribs and deep 

 intermediate furrows, which extend to the inside of the valves, 

 terminating in regular crenulations on the margins ; the 

 convex valve provided with irregularly set, somewhat dis- 

 tant, curved, and long spines, each of which has a dorsal ridge 

 and a furrow beneath ; some of those nearest the base of the 

 shell are equal to half the length of the valve, whole surface 

 covered with very fine, raised, transverse striae. 



Upper Chalk, Northfleet, Lewis, Norfolk, and Wiltshire. 



3. Plagiostoma punctatom. — The Punctured Plagios- 

 toraa, pi. LXVI. fig. 19. 



P. punctata. Sowerby, II. p. 25, pi. 113, figs. 1, 2. Lima. 

 Goldfuss, p. 81, pi. 101, fig. 2. 



Obliquely obovate, compressed ; anterior side long and 

 nearly straight ; ears nearly equal ; whole surface covered with 

 numerous, nearly regular, longitudinal coarse strioe, and very 

 fine transverse stria), which produces a somewhat punctated 

 appearance. 



Inferior Oolite, Cotswold Hills, Lias, Weston, and Picke- 

 ridge Hill. 



4. Plagiostoma elongatum, — The Elongated Plagios- 

 toma, pi. LXVI. fig. 4. 



Modiola parallela. Sowerby, I. p. 31, pi. 9. Upper right- 

 hand figure, lb. VI. p. 113, pi. 559, fig. 2, 



Transversely elongated, nearly twice as broad as long, acutely 

 convex, anterior and posterior sides parallel ; beaks rather 

 sharp ; lower margin straight, short, and nearly at right angles 

 with the sides, which are almost straight and parallel ; surface 

 with a few transverse furrows. 



The Gualt, Folkstone and Ridge; the Lower Greensand, 

 Artherfield Point, Isle of Wight, and Court-at-Street. 



5. Plagiostoma concentbicum. — The Concentric Plagios- 

 toma, pi. LXVI. fig. 2. 



P. cancentrica. Sowerby, VI. p. 113, pi. 559, fig. 1. 



Aricula ocatis. Phillips, Geo. York, I. pi. 3, fig. 36 (?) 



Obliquely elliptical, convex, most so towards the beaks, 

 hinge-line short and oblique ; surface with numerous longi- 

 tudinal divergent strioe, and a few concentrical lines of growth ; 

 beaks slightly produced ; shell thick. 



The Lias, Ethie, Cromarty. 



6. Plagiostoma duplicatim. — The Double-Plaited Pla- 

 giostoma, pi. LXVI. fig. 6. 



P. dufilieata. Sowerby, pi. 559, fig. 3, Phillips, (ieo. York, 

 I. pi. 6, fig. 2. 



Obliquely oboval, convex ; beaks rather produced ; surface 

 with numerous sharp, divergent ribs, with a shaqi elerated 



line intervening between each. The ribs are about twenty-five 

 in number. 



The Coral Rag, Malton and Scarborough, the Kelloways 

 Rock, Hackness, and the Lias, Brodon and Weston. 



7. Plagiostoma Hoperi. — Hoper's Plagiostoma, pi. LXVI. 

 fig. 18. 



P. Hoperi. Sowerby, IV. p. Ill, pi. 380. 



Transversely and obliquely ovate; convex; almost smooth ; 

 surface with very slender, nearly obsolete, divergent, obscurely 

 puntated strite, which are strongest at the sides ; anterior side 

 stra'ght and a little concave, ears unequal, small, with longi- 

 tudinal strice. 



The Chalk, Lewis and Norwich, and the Upper Greensand, 

 Isle of Wight. 



8. Plagiostoma rusticum. — The Rude Plagiostoma, pi. 

 LXVI. fig. 1. 



P. rusticum. Sowerby, IV. p. Ill, pi. 381. 



Transversely oblong-ovate, oblique, smooth, convex, hinge- 

 line very short, ears obscure and very short, the anterior side 

 straight, convex along the middle, surface with about twenty- 

 five deep, irregular, strong, somewhat waved, divergent, longi- 

 tudinal furrows; beak a little prominent. 



The Portland Stone, Great Hazely, Oxfordshire, and the 

 Coral Rag, JIalton and Shotover. 



9. Plagiostoma laeviusculum. — The Smooth Plagios- 

 toma, pi. LXVI. fig. 17. 



P. Ifeoiuscultcm. Sowerby, IV. p. 112, 382. 



Subtriangular, oblique, its length exceeding its breadth, 

 hinge-line oblique, short, and intercepted ; ears small, un- 

 equal, longitudinally furrowed ; anterior side straight, whole 

 surface covered with many large, slightly elevated, longi- 

 tudinal, divergent ribs, and numerous irregularly elevated 

 concentric lines of growth ; margin slightly scolloped. 



The Coral Rag, Malton, Yorkshire. 



10. Plagiostoma rigidum. — The Rigid Plagiostoma, pi. 

 LXVI. fig. 5. 



P. riffidum. Sowerby, II. p. 27, pi- 114, fig. 1. 



Inflated, obliquely obovate ; hinge-line rather long, and 

 considerably oblique, ears narrow and nearly e<(ual ; anterior 

 side long, straight, and a little concave ; posterior side round- 

 ed, beaks obtuse, surface with numerous, sharp, irregularly 

 undulating throad-likc, longitudin.al, divergent ribs, with very 

 minute, intervening stri;u, which cannot be discerned without 

 the use of a lens ; beaks rather produced. 



The Lower Greensand, North Wiltshire, and the Coral 

 Rag, Malton and Shotover. 



n. Plagiostoma ovale. — The Oval Plagiostoma. pi. 

 LXVI. fig. 13. 



P. oralis. Sowerby, II. p. 27, pi. 114, fig. 3. 



Somewhat vontricose, elongated, moderately oblique ; sides 

 nearly equal, the anterior one a little concave, and slightly 

 recurved, ears rather large ; surface with numerous small 

 rounded, equidistant, divergent ribs, and the intervening: 

 spaces, with minute, transverse strite. 



The Great Oolite, near Bath. 



12. PLAfiiosTOMA ouscurdm. — The Obscure Plagiostoma, 

 pi. LXVI. fig. 3. 



P. Obicura. Sowerby, II. p. 28, pi. 114, fig. 2. 



