188 



CONCHIFERA. 



KCTUNCULUS. 



N. niida. Phillips, Geo. York, I. pi. 5, fig. 5. 



Transversely elongated ; anterior side short ; posterior side 

 elongated ; beaks obtuse ; surface smooth ; base a very little 

 curved. 



Oxford Clay, Scarborough. 



50. NucuLA L^viROSTRA. — The Smooth-beaked Nucula, 

 pi. LXXVI. fig. 71. 



N. Iwvirostrum. Portlock, Geo. Sur. p. 439, pi. 36, f. 12. 



Oblong-ovate, club-shaped ; anterior side short and rounded ; 

 posterior side lengthened and obtuse ; beaks obtuse ; surface 

 with fine concentric strioe. 



The Carboniferous Limestone, Tyrone and Armagh, Ireland. 



51. Nucula latissima. — The Very-broad Nucula, pi. 

 LXXVI. fig. 73. 



N. latissima. Phillips, Pal. Fos. p. 137, pi. 58, fig. 65.* 

 Oblong-ovate ; both extremities almost equally round, with 

 a slightly produced angle superiorly. 

 The Devonian Shales at Pelton. 



52. Nucula pygMvEA. — The Pigmy Nucula, pi. LXXVI. 

 figs. 66, 67. 



N. pyf)m(ea. Goldfuss, pi. 125, fig. 17. N. gihhosa. Forbes, 

 Wern. Tr. VIII. pi. 2, fig. 10, 10.* (?) 



Sub-triangular ; anterior side a little pointed ; posterior side 

 slightly rounded ; base much arcuated ; beaks obtuse ; surface 

 smooth. 



The Pleistocene Marine Formations, Greenock Railway, 

 and the Coral Crag, Ramshot and Sutton. 



53. Nucula plicata. — The Plicated Nucula, pi. LXXVI. 

 fig. 62. 



N. plicata. Phillips, Pal. Fos. p. 38, pi. 18, fig. 63. 



Obliquely ovate, compressed ; beaks prominent ; surface 

 smooth, shining, concentrically striated, with the posterior area 

 finely plicated. 



The Devonian Shales, Boggy Point. 



54. Nucula kadiata. — The Rayed Nucula, pi. LXXVI. 

 fig. 65. 



iV". (?) radiata. Portlock, Geo. Rep. p. 430, pi. 36, fig. 11. 



Transversely elongated ; anterior side rounded ; posterior 

 side acute, and obliquely truncated, and with a ridge emanat- 

 ing from the beak, and terminating on the side ; the flattened 

 space with radiating thread-like stripe ; beaks well defined. 



The Silurian Rocks, Tyrone, Ireland. 



55. Nucula minuta. — The Minute Nucula. 



N. minuta. Brown, Rec. Conch. Brit. p. 84, pi. 33, fig. 18. 



Transversely elongated ; anterior side rounded ; posterior 

 side produced, acuminated, sub-truncated, and a little curved 

 upwards ; surface with strong, transverse striae. 



The Pleistocene Marine Formation, Dalmuir, and the Red 

 Crag, Sutton. 



56. Nucula nucleus. — The Kernal Nucula. 



N. margaritacea. Brown, Rec. Conch. Brit. p. 85, pi. 33, 

 fig. 12. 



Ovate ; both sides rounded ; beaks near the anterior side ; 

 surface with numerous fine lines of growth. 



The Pleistocene Marine Formations, Ayr, and the Red 

 Crag, Sutton. 



57. Nucula rostrata. — The Beaked Nucula. 



N. rostrata. Brown, Rec. Conch. Brit. p. 84, pi. 33, f. 16. 

 Transversely elongated ; auterior side rounded ; posterior 



side produced and curved upwards, and transversely striated ; 

 surface slightly ribbed longitudinally, and obliquely crossed by 

 the striae. 



The Pleistocene Marine Formations, Sutton, &c. 



58. Nucula tenuis. — The Thin Nucula. 



N. tenuis. Brown, Rec. Conch. Brit. p. 85, pi. 33, fig. 13. 



Obliquely ovate ; both sides rounded ; surface smooth and 

 shining. 



Pleistocene Marine Formation, Dalmuir and Paisley ; the 

 Mammiferous Crag, Southwold, and the Red Crag, Bawdsey. 



59. Nucula oblongoides. — The Oblong Nucula, pi. 

 LXXVI. figs. 84, 85. 



Wood, Mag. Nat. Hist. 1840, p. 297, pi. 14, fig. 4. 



Transversely ovate, lanceolate ; somewhat inequilateral, the 

 anterior side rounded; posterior side acuminated ; lunule lan- 

 ceolate ; surface smooth. 



Mammiferous Crag, Bramerton, and the Red Crag, Butley. 



60. Nucula semi-striata. — The Half-striated Nucula, pi. 

 LXXVI. figs. 86, 87. 



N. semi-striata. Wood, Mag. Nat. Hist. 1840, p. 297, pi. 

 14, fig. 5. 



Transversely ovate ; somewhat inequilateral ; anterior side 

 rounded and smooth ; posterior side acuminated, and trans- 

 versely striated ; substance of the shell thin. 



The Coral Crag, Sutton. 



61. Nucula trigonula. — TheTrigonal Nucula,pl. LXXVI. 

 figs. 88, 89. 



N. trigotiula. Wood, Mag. Nat. Hist. 1840, p. 295, pi. 

 14, fig. 3. 



Obliquely ovate, deltoidal, tumid ; beaks prominent ; lunula 

 embedded ; convex in the middle ; surface smooth ; internal 

 margin cronulated ; longitudinal diameter three sixteenths, 

 transverse diameter a quarter of an inch. 



The Coralline Crag, Sutton. 



Genus VIII.— PLEURODON.— >9. Wood. 



Shell bivalve, inequilateral ; hinge-line curved ; several 

 uniform, converging, cardinal teeth placed in a row, immedi- 

 ately under the umbo ; one large lateral tooth, situate poste- 

 riorly ; ligament external. 



1. Pleurodon ovalis. — PL LXI.*** figs. 24, 25. 



P. ovalis. Wood, Mag. Nat. Hist. 1840, p. 230, pi. 13, fig. 

 1. Nucula miliaris (?) Deshayes, Foss. des En v. de Paris, 

 pi. 36, figs. 7, 8, 9. 



Ovate, deltoidal, gibbose, sub-orbicular ; smooth, margin en- 

 tire ; hinge with five or six converging cardinal teeth, and a 

 large lateral tooth in each anterior side of the valves ; large.st 

 diameter three thirty-seconds of an inch. 



Genus IX.— PECTUNCULUS.—Zrtma>-<;/!-. 



Shell orbicular, sub-equilateral, with the valves close ; uni- 

 bones near to each other, and separated by a narrow facet or 

 area ; hinge semicircular ; teeth numerous, arcuated, oblique. 



