110 



MOLLUSCA. 



Spirifer. 



elevated above the hinge line ; front roundeil, with an elevated 

 mesial fold, on each side of which is a deep furrow ; whole 

 surface covered with numerous, linear furrows, which increase 

 in number towards the margin, the spaces between the furrows 

 ill the form of thin brancliod ribs. 



The Carboniferous Limestone near Dublin. 



22. Si'iBiFEB UNDILATUS. — The Waved Spirifer, pi. L. 



fig. 27, 28. 



Spirifer undulalus. Sowerby, M. p. 1 19, pi. 562, fig. 1. 



Convex, transversely elongated, its width being twice its 

 length ; cardinal area flat, rather narrow, with almost parallel 

 edges, and acute at the extremities; beaks approximate, and 

 not much elevated; mesial elevation rather inflated, and round- 

 ed ; whole surface with numerous, well defined, longitudinal 

 ribs, sixteen on each side of the mesial sinus, crossed by deep, 

 wide-set, regular stria:, which are semicircular in passing over 

 the ribs. 



From the Magnesian Limestone at East Thickly, West Auk- 

 land, County of Durham. 



23. Spirifer semicirculabis. — The Semicircular Spirifer, 

 pi. L. fig. 23, 24. 



Spirifer semicircularia. Phillips, IL p. 2 1 7, pi- 9, fig- 1 5, 1 6. 



Upper valve nearly semicircular ; cardinal area variable in 

 width, sharp at the extremities ; beaks rather obtuse ; mesial 

 fold very broad, and sulcated ; surface with smooth, radiating, 

 longitudinal ribs, fifteen or sixteen on each side of the mesial 

 fold, and divarigated at their base. 



Subject to a little variety ; some with the cardinal area rectan^lar, 

 and others acute. 



Mountain Limestone at Chipping; Whitewell, Queen's Coun- 

 ty, Ireland ; and Isle of Man. 



24. Spirifer plicatus. — The Plaited Spirifer, pi. LII.* 

 fig. L 



Spirijlr plicatus. Murchison, p. 638, pi. 21, fig. 6. 



Semicircular, convex ; cardinal area long, narrow, extending 

 to nearly double the length of the shell ; whole surface with 

 wide-set, divergent plaits ; beaks approximate. Length eleven 

 lines ; breadth one inch and seven lines. 



Cardoc Sandstone, Goleugoed and Llandovery, Wales. 



25. Spiuifeu alatus. — The Winged Spirifer, pi. LII.* 

 fig. 3, 4. 



Spirifer alatus. Murchison, p. 638, pi. 22, fig. 7. 



Semicircular; cardinal area long, narrow, terminating in con- 

 siderably expanded, cuspidate sides ; centre of the valves a little 

 inflated ; whole surface with about eighteen acute plaits. 

 Length five lines and a half; width nine lines and a half. 



Cardoc Sandstone, Pensarn and Mount Pleasant, Caermar- 

 then. 



20. Spirifer pinnatds. — The Pointed Spirifer, pi. LII.* 

 fig. 4, 5. 



Spirifer alatus. Murchison, pi. 22, fig. 7, the lower figs. 



Transverse, oblique, somewhat semicircular ; hinge line 

 straight, very narrow, and prolonged to an acute point at both 

 sides, one side more lengthened than the other ; beaks a little 

 elevated ; nurfacc with numerous, divergent plaits. 



Thi» (lifTcri from S. alalut, in licing murli longer in proportion to its 

 breadtli, nnd in being a little oWi<iuc, with one winif longer and more 

 acute than the other. 



Cardoc Sandstone, Mount Pleasant, Caerrnarlhen. 



27. Spirifer humerosa. — The Hooded Spirifer, pi. LI. 

 fig. 3. 



Spirifera humerosa. Phillips, II. p. 218, pi. 11, fig. 8. 



Subcordiform ; lower valve very large, and very turgid near 

 the umbones, with a produced mesial fold, which receives the 

 angular and elevated ridge of the upper valve ; surface with 

 numerous, small, longitudinal, divergent ribs. 



Mountain Limestone, Greenhow Hill, Yorkshire. 



Section III — Radiate — Cardinal area not so wide 

 as the shell ; surface radiated. 



28. Spirifer lineatus — The Lineated Spirifer, pi. L. 

 fig. 6, 7. 



Spirifer lineatus, Sowerby, V. p. 151, pi. 493, fig. 1, 2. 

 Fleming, p. 375. 



Gibbose ; umbones produced, somewhat remote, with their 

 beaks approximate; cardinal area long, rounded, rather narrow, 

 and with a triangular foramen; front semicircular, with a pretty 

 elevated, mesial fold, ending in the beak ; whole surface with 

 numerous, divergent, sharp, granulated stria?. Breadth some- 

 what more than its length. 



Dudley Limestone at Dudley. 



29. Spirifer ovalis. — The Oval Spirifer, pi. LI. fig. I. 



Spirfera ovalis. Phillips, II. p. 219, pi- 10, fig. 5. 



Elliptical ; cardinal area triangular ; umbones produced, in- 

 curved ; mesial fold large, obtusely rounded, spreading widely at 

 the base; with six or seven pretty broad ribs on each side. 



Mountain Limestone, BoUand. 



30. Spirifer planata. — The Plane Spirifer, pi. LI. fig. 6. 

 Spirifera pkmata. Phillips, II. p. 219, pi. 10, fig. 3. 

 Suborbicular ; cardinal area rather wide ; umbones obtuse, 



and remole; surface with numerous, flat, plain ribs; upper 

 valve nearly plane. 



Mountain Limestone, BoUand. 



31. Spirifer trisulcosa. — The Three-furrowed Spirifer. 

 pi. LI. fig. 9. 



Spirifera trisulcosa. Phillips, II. p. 219, pi. 10, fig. 6. 



Elongated, rather smooth ; beaks produced ; cardinal area 

 subtriangular ; upper valve with a pretty large, produced, mesial 

 fold, and a lateral plait on each side. 



Mountain Limestone, BoUand. 



32. Spirifer integricosta. — The Inter-ribbed Spirifer, 

 pi. LI. fig. 8. 



Sjiirifera integricosta. Phillips, II. p. 219, pi. 10, fig. 2. 



Nearly orbicular, and greatly inflated ; umbones large, much 

 curved, the beaks nearly meeting; mesial fold of medium size; 

 longitudinal ribs few, obtuse, entire, and smooth. 



Mountain Limestone, BoUand and Northumberland. 



33. Spirifer triradialis — The Three-rayed Spirifer, pi. 

 LI. fig. 10. 



Spirifera triradialis. Phillips, II. p. 219, pi. 10, fig. 7. 



Orbicular, smooth ; beaks of under valve large, incurved ; 

 upper valve depressed, with a broad mesial fold and a lateral 

 fold on each side. 



Mountain Limestone, Bolland. 



34. Spirifer sexradialis — The Six-rayed Spirifer, pi. 

 LI. fig. 17. 



Spirifera sexradialis. Phillips, II. p. 219, pi- 10, fig. 8. 



