Moi: 



CONCH IFERA. 



17o 



posterior section of tiio sbell ; rournlcd and narrowcil anterior- 

 ly ; expanded postcrinrly, with an oljliquo curved truncation. 

 The Silurian Hocks, Tyrone, Ireland. 



42. MoDioLA SEcuiiiFoiiMis. — Tho Axe-sbapod Modiola. 

 A. lecuri/onnis. Portlock, Geo. Sur. p. 425, pi. 33, f. 8. 

 Elongated ; anterior side narrowed and rounded ; posterior 



side expanded and rounded, but destitute of the obliijue trun- 

 cation ; an oblique ridge extends from tbc beak to tlie poste- 

 rior margin. 



The Silurian Rocks, Tyrone, Ireland. 



43. Modiola Brycei. — Bryce's Modiola. 



M. Brycei. Portlock, Geo. Rep. p. 425, pi. 33, fig. 7. 



Attenuated and rounded anteriorly j hinge-line rather ex- 

 tended ; the diagonal ridge strongly marked ; surface smooth, 

 with faint-lines of growth. 



The Silurian Rocks, Tyrone, Ireland. 



44. Modiola carinata. — The Keeled Modiola, pi. LXI.-'** 

 figs. 19, 20. 



M. carinata. Sowcrby, Geo. Tr. 2d Ser. V. jil. 3.9, fig. 15. 



Obliquely elongated, ventricose, boat-shaped ; valves deep ; 

 anterior side short ; posterior side lengthened ; beaks obtuse ; 

 an abrupt carinated ridge extending from the beaks to the 

 posterior lower angle of the valves ; surface with a few obso- 

 lete lines of growth. 



The Coal Measures, Coalbrook Dale. 



45. Modiola MACADAMi.—Macadam's Modiola, pi. LXI.*''* 

 figs. 14, 15, 16. 



M. Macadami. Portlock, Geo. Rep. p. 432, pi. 34, figs. 

 13, 14, 15. 



Variety \.—Angueta, pi. LXI.*** fig. 14. Portk. pi. 34, fig. 1,3. 



Lengthened, narrow, convex, somewhat cylindrical, but 

 wider behind than before ; beaks obscure, situate very near 

 the anterior side ; front rounded, and with a slight obliquity 

 in the posterior margin ; hinge-line straight, but not distinct ; 

 surface with fine concentric striaj. 



" This diverges as much from the ordin.iry form in one direction as 

 fig. 15 does in another." — Porthrk. 



Varietv 2.—Elongaia, pi. LXI.*** fig. 15 Portk. pi. 31, fig. 14. 



Elongated ; narrowed at both extremities ; beaks quite de- 

 pressed ; binge-lino straight, oblique, terminating in an angle, 

 and equal to about half the length of tho shell ; from thence 

 the side grailually slopes downwards; surface with fine raised 

 thread-like stria). 



" This approximates to Mcniiola linijual'is (Phillips.)" — Portlock. 



Variety 3.— i'/ta, pi. LXI.*" fig. IC. Portk. pi. 34, fig. 15. 



Ovate ; beaks obsolete ; hinge-line straight, and exceeding 

 one-half tho length of the shells, and terminating in an angle ; 

 anterior side extremely short and rounded ; posterior side ex- 

 panded and compressed ; surface wrinkled on the anterior side 

 and at the beaks, and exhibiting the appearance of the shell 

 having been originally covered with concentric thread-like 

 raised stria-. 



" The flattened form is probably the result of pressure, as it is rare ; 

 and the ordinary form exhibits a more distinct rise, or rounded ridge, 

 from the beak to the posterior margin, and is narrower." — Porl/uck. 



The Carboniferous Limestone, Ballynascreen, Dorry and 

 Tyrone. 



If fonn goes for anything, the three varieties of this shell would appear 

 to be distinct ; and looking at the lines of growth on figs. 14 & 15, we 

 cannot see how they could a^sme the form of fig. 10. 



46. IMoDioLA GRANULOSA. — The Granular Modiola. 



M. ffranulosa. Piiillips, Geo. York, II. p. 210, pi. 5, f. 23. 



" Very much elongated, depressed ; surface granulose." — 



The Carboniferous Limestone, Bolland and Northumber- 

 land. 



47. Modiola Nerki. — Neres Modiola, pi. LXI.*''-'" f. 17. 

 M. Nerei. MylilisQ.) Nerei. Munster, Beit. 1840, pi. 11, 



fig. 14; Portlock, Geo. Rep. p. 424, pi. 33, fig. 10. 



Obovate, convex, thick ; beaks terminal, a little produced ; 

 sides almost e(jual, curved, and the basal extremity rounded ; 

 hinge-line straight ; surface with fine regular concentric stria;. 



The Silurian Rocks, Desertcreat, Tyrone, Ireland. 



48. Modiola marmorata. — The Marbled Modiola. 



M. marmorata. Brown, Recent Conch. Brit. & Ir. p. 78, 

 pi. 27, fig. ] 0. M. discors. Turton, p. 210, pi. 15, figs. 4, 5. 



Oval, very tumid ; anterior side a little pointed ; beaks 

 terminal, rounded, and somewhat convolute ; centre of the 

 valves a little constricted towards the margin ; surface smooth, 

 with a scries of longitudinal divergent grooves at both sides, 

 and slightly striated transversely at the pointed extremity. 



The Pleistocene Marine Formation, Ayrshire, and the 

 Coral Crag, Sutton. 



49. Modiola sub-parallela. — The Sub-parallel Modiola, 

 pi. LXI.-""- fig. 18. 



M. sub-parallela. Portlock, Geo. Rep. p. 433, pi. 34, f. 16. 



Oblong-ovate; convex; beaks obtuse ; liinge-Iine long and 

 nearly straight ; anterior side short, the posterior long ; both 

 extremities almost equally rounded ; with a slight contraction 

 from the beaks to the margin, forming an obscure anterior lobe ; 

 a diagonal rise from the beak to the margin, not constituting 

 a ridge ; surface with somewhat irregular thread-liko con- 

 centric striae. 



Tho Carboniferous Limestone, Ballynascreen, Tyrone, Ire- 

 land. 



50. Modiola scalaris. — The Ladder Modiola. 



M. scalaris. Phillips, Pal. Fos. p. 137, pi. 60, fig. 62.* 

 " Dojiressed, transversely elongated to a parallelogramie 

 figure, with elliptical terminations ; front edge straightened, 

 or slightly sub-concave near the middle ; surface ridged by 

 about fifteen elevated narrow threads, p,arallol to the margin, 

 separated by wider flat spaces, in which are fine striaj parallel 

 to the elevated threads." — Phillips. 



Devonian Shales, Berry Pomeroy, South Devon. 



51. Modiola pai'ia.na. — The Common Modiola. 



M. papuaiia. Brown, lUust. Rec. Conch. Brit. p. 77, j)!- 

 27, figs. 1, 2, 3, 4, 5, 6. 



Transversely oblong ; anterior side short ; posterior side 

 lengthened, dilated, and rounded ; beaks tumid and obtusely 

 angular ; surface smooth. 



The Mammiferous Crag, Postwick. 



52. Modiola acu.mi.vata.— (ScJirariy, Geo. Tr. 2d Si'i-. 

 III. p.ll9.— Not described. 



The .Magnesian Limestone, lluuibleton, Durham. 



53. Modiola decussata. — The Decussated Modiola, pi. 

 LXI.*"- figs. 22, 23. 



M. (?) Jelly, Mag. Nat. Hist. III. New Ser. p. 551, fig. 

 69. I. c. 



