AVICULA. 



CONCHIFERA. 



163 



a: qtiadrata. Sowerby, Geo. Tr. 2d Ser. V. pJ. 39, fig. 1". 



Sub-quadrangular, convex ; hingo-linc straight ; .anterior 

 auricle small, rounded ; posterior auricle not defined ; a keel 

 extending from the beak to the basal margin, which is 

 rounded. 



The Coal Jleasures, Coalbrook Dale. 



40. AvicuLA DiscoRs. — The Discordant Avicula, pi. 

 LXA'I.** fig. 3. 



A. diseors. Brown, Trans. Manch. Geo. Soc. I. p. 56, pi. 

 VI. fig. 28. 



Smooth, obliijue ; anterior side short acute, posterior side 

 broad; sujiorior auricle large; the inferior one small and 

 parallel with the hinge-line ; beaks small and prominent ; 

 length a quarter of an inch ; breadth nearly three-eighths. 



The New Eed Sandstone, Newton, near Manchester. 



41. Avicula ANTiQUA. — The Ancient Avicula, pi. LXI.** 

 fig. 5. 



A. antiqua. Goldfuss, pi. IGO, fig. .9. 



Obliquely sub-orbicular; hinge-line straight; auricles rather 

 large ; the anterior slightly defined ; the posteri(Jr one large ; 

 concave on the edge ; whole surface with numerous, longitu- 

 dinal, oblique, divergent strong ribs, with from one to three 

 smaller intervening ones ; crossed by many concentric, broad, 

 shallow lines of growth. 



Upper Silurian Limestone, Westmoreland. 



42. Avicula lunulata. — The Crescent-shaped Avicula, pi. 

 LXA^II. fig. 17. 



GerpiUia huiulata. Phillips, Geo. York, II. p. 211, pi. 

 6, fig. 12. 



Very oblique, and much arcuated ; hinge-line greatly ob- 

 lique ; auricles unequal ; the anterior one short and blunt ; the 

 posterior very long, and acute at the upper angle ; posterior 

 side much lengthened, and with pretty strong concentric 

 ridges; anterior side short; the beaks obtuse; surface with 

 slight imbricated stria". 



The Carboniferous Limestone, Bolland. 



*3. A viculaNeptune. — Neptune's Avicula, pi. LXI.** f. 2 1 . 



Sub-orbicular, sub-compressed ; hinge-line horizontal ; auri- 

 cles unequally undefined; anterior one short; posterior 

 projecting, in a line with the side, and acute ; whole surface 

 with numerous, divergent, rounded, narrow ribs, with some- 

 times smaller intervening ones ; crossed by very close, numer- 

 ous concentric, raised stria; ; anterior side rounded ; posterior 

 side rather straight. 



The Upper Silurian Limestone, "Westmoreland. 



44. Avicula te.nera The Tender Avicula, pi. LXI.** f. 11. 



A. paj»/racen. Goldfuss, pi. CXVI. fig. 5. 



Sub-orliicular, oblique ; hinge-line nearly horizontal ; auri- 

 cles unequal ; the anterior small and well defined ; the poste- 

 rior large and undefined ; concave on the edge ; whole sur- 

 face covered with numerous oblique, divergent, somewhat 

 unequal ribs, most of them with a central groove, the ribs as 

 well as the intervening furrows crossed by numerous close-set, 

 strong stri.T ; sides and base rounded. 



The Coal ^Measures, Bradford. 



4;j. Avicula pectinata. — The Pectinated Avicula, pi. 

 LXVI.»* fig. 2. 



A.pectinata. Sowerby, Geo. Trans. 2d. Ser. IV. p. 338. 

 pi. H, fig. 3. 



Obliquely-elongated, slightly arcuated, and a little convex ; 

 hinge-line straight and horizontal; beaks obtuse and produced 

 above the hinge area ; auricles large ; the posterior one con- 

 cave on the margin, as well as on the side of the valve ; ante- 

 rior side convex and rounded, and surface with alternately 

 long and short linear ridges. 



The Lower Greensand, Risborouijh, Kent. 



46". Avicula simplex. — The Siuiple-ribbed Avicula, pi. 

 LXV. figs. 26, 27. 



Pecten simple JC. Phillips, Geo. York, II. p. 212, pi. C, fig. 

 27. 



Obliquely-elongated ; hinge-line straight and oblique ; auri- 

 cles nearly equal ; lower valve tumid ; the surface with strong 

 divergent ribs and furrows ; upper valve rather flat, with 

 the furrows and ribs corresponding to the other, but shallower 

 and flatter. 



The Carboniferous Limestone, Bolland. 



47. Avicula sub-radiata. — The Sub-rayed Avicula, pi. 

 LXL** fig. 29. 



A. sub-radiata. Sowerby, Geo. Tr. 2d Ser. V. pi. 34, fig. 1. 

 Phillips, Pal. Foss. pi. 23, fig. 86. 



Obliquely and transversely elongated ; breadth extending 

 the whole length of the shell ; hinge-line horizontal ; one 

 valve flat, the other convex ; auricles not defined, the poste- 

 rior one smooth, with a few concentric lines, with radiations 

 along the middle ; anterior side narrow and pointed ; poste- 

 rior side broad, and a little concave ; surface with remote ra- 

 diating lines, crossed by raised concentric lines of growth. 



The Devonian Shales, Petherwin. 



48. Avicula cygxipes. — The Swan's-foot Avicula, pi. 

 LXVI.** fig. 17. 



A, ciignipes. Phillips, Geo. York, I. p. 134, pi. 14, fig. 

 3. Pecten cygnipes. Young and Bird, Geo. Sur. York, 

 Coast, p. 235, pi. .9, figs. 4 and 6. 



Sub-quadrate, oblique ; lower valve convex, the other flat ; 

 hinge-line straight, oblique ; umbo of the convex valve 

 rounded and obtuse, projecting above the hinge area ; auricles 

 very unequal, the anterior one exceedingly small and pointed ; 

 the posterior one very large, concave on the edge, the point 

 obtuse, and protruding beyond the side ; surface with from 

 four to five longitudinal, divergent, curved ribs, inclining pos- 

 teriorly, and extending half an inch beyond the margins, ter- 

 minating in acute points; the intercostal spaces covered with 

 fine longitudinal stria; ; lower margin concave between the 

 ribs ; flat valve with furrows corresponding in number to the 

 ribs of the other valve, and with rather coarser, longitudinal 

 striic between the furrows, and with a few concentric lines of 

 growth towards the base, the auricles and hinge-line corre- 

 sponding with the under valve. 



The Ironstone Bands in the Aluminous Strata, near Whitby, 

 and in the Lias at Bilsdalo and Wilton Castle, Yorkshire. 



49. Avicula lonoico.stata. — The ],ong-liibbcd Avicula, 

 pi. LXVI.*^^ figs. 1.5, 16. 



A. hngicostata. Stutchbury, Mag. Nat. Hist. 1839, p. 163, 



fig. 28. 



Ovate, inecpiivalve, the lower one convex and the upper 

 flat; lower valve with the hinge-lino horizontal, and a little 

 curved ; ears very unequal, the anterior one extremely small 

 and obtuse, the posterior very large, somewhat rounded 



