162 



CONCHIFERA. 



AviCULA. 



26. AvicuLA MODioLiFORME. — The Modiolaforraed Avicula, 

 pi. LXVI.- fig. 19. 



A.modiola. Rliind, Age of the Earth, p. 167, pi. 2, fig. 5. 



Much elongated transversely ; unibones placed near one 

 side, gradually widening towards the opposite side ; hinge-line 

 not defined, a triangular small ear on one side ; surface trans- 

 versely wrinkled. 



The Coal Shale, Woodhall, on the River Leith, near Edin- 

 burgh. 



27. Avicula novemcostae. — The Nine-Ribbed Avicula, 

 pi. LXVI.*-- fig. 12. 



A. inaequicalvis. Phillips, Geo. York, I. p. 133, pi. \i, 

 fig. 4. 



Obliquely oval ; hinge-line slightly oblique ; one ear very 

 small, the other large ; surface smooth, with nine longitudinal 

 rounded, divergent ribs, gradually thickening from the beaks to 

 ^ the basal margin. 



The Marlstone, in many localities. 



28. Avicula expansa. — The Expanded Avicula, pi. 

 LXVI.**fig. 13. 



A. expansa. Phillips, Geo. York, I. pi. 3, fig. 35. 



Oblong-ovate, very oblique ; the posterior side extremely 

 produced ; anterior side short and gently curved ; auricles 

 well defined, very unequal ; the anterior one very small, and 

 the posterior one large, curved on the side ; hinge-line a little 

 oblique; surface smooth, with about sixteen rounded, divergent, 

 longitudinal ribs. 



The Coral Rag, Malton, the Kelloways Rock, South Cove, 

 and Oxford Clay, Scarborough. 



29. Avicula ovalis.— The Oval Avicula, LXVI.** 

 fig. 14. 



A. oealis. Phillips, Geo. York, I. pi. 3, fig. 36. 



Oblong-ovate ; ears unequal, the anterior one about half the 

 size of the other ; binge-line considerably oblique and straight ; 

 beaks produced ; sides a little unequal, gently rounded ; sur- 

 face with numerous, divergent, shallow, longitudinal furrows, 

 and a few concentric, shallow lines of growth. 



The Coral Rag, Yorkshire. 



30. Avicula decbpta. — The Deceptive Avicula, pi. 

 LXXXIII. fig. 18. 



Obliquely transverse ; hinge-line nearly straight ; auricles 

 undefined ; the anterior one acute ; lower part of the dorsal 

 side produced ; umbones obsolete ; surface transversely 

 wrinkled. 



The Coal Shale, Vale of Todmorden. 



31. Anomia gryphoides. — The Graphite Avicula, pi. 

 LXYI."-^- fig. 19, 20. 



A. ffn/pkoides. Sowerby, Geo. Tr. 2d Ser. IV. p. 335, pi. 

 11, fig. 3. . 



Obliquely elongated ; the convex valve ovate, with a pro- 

 duced, incurved beak, and two small nearly equal auricles ; 

 upper valve nearly flat, suborbicular, and furnished with a 

 single auricle. 



The Upper Greensaml, near Petersfield. 



32. Avicula elegantissima. — The Very Elegant Avicula, 

 pi. LXVI.-- fig. 21. 



.4. elegantmitna. Phillips, Geo. York, I. pi. 4, fig. 2. 

 Transversely elongated ; its breadth twice and a half its 

 length ; hiuge-line a little hollowed ; beaks produced, large. 



rounded, and situate near the anterior side, which is extremely 

 short, and almost straight ; posterior side much elongated, 

 with a large auricle, nearly equal to half the breadth of the 

 shell ; surface smooth, and provided with from seven to nine 

 divergent, longitudinal, smooth ribs in the centre of the 

 valves. 



The Coral Rag, Malton. 



33. Avicula eadiata. — The Rayed Avicula, pi. LXVI.** 

 fig. 30, 



A. radiata. Phillips, Geo. York, II. p. 211, pi. 6, fig. 8. 



Sub -orbicular ; hinge-line straight ; beaks nearly central; 

 auricles unequal, acute, and extending beyond the sides of the 

 valves ; surface with many radiating, rather broad ribs, and 

 narrow intervening furrows ; base rounded. 



The Carboniferous Limestone, BoUand. 



34. Avicula cycloptera. — The Cyclops Avicula, pi. 

 LXVI.** fig. 34. 



A. cycloptera. Phillips, Geo. York, II. p. 211, pi. 6, fig. 5. 



Sub-quadrangular; hinge-line sloping downwards from both 

 sides of tiie beak ; sides a little conical ; surface smooth, with 

 four or five radiating ridges, arising a little below the beaks, 

 and terminating on the rounded and scolloped basal margin ; 

 lines of growth slightly imbricated on the disk of the valves. 



The Carboniferous Limestone, Bolland. 



35. Avicula te.ssellata. — The Tessellated Avicula, pi. 

 LXVI.** fig. 31. 



A. tessellatta. Phillips, Geo. York, II. p. 211, pi. 6, fig. 6. 



Sub-quadrangular; hinge-line slightly curving downwards 

 from the beak, and extending beyond the sides ; auricles very 

 large, unequal, and subacute ; surface with from eight to fif- 

 teen radiating rounded ridges, extending beyond the basal 

 margin, producing a scolloped edge. 



The Carboniferous Limestone, Bolland and Colster Dale. 



36. Avicula sublobata. — The Half-lobed Avicula, pi. 

 LXVI.*" fig. 32. 



A. suhloliata. Phillips, Geo. York, II. p. 211, pi. 6, 

 fig. 25. 



Oval, slightly oblique ; hinge-line short, straight, with a 

 small auricle on one side ; surface with numerous divergent, 

 flat, narrow ribs, the intermediate furrows with fine concentric 

 stria. 



The Carboniferous Limestone, Castleton, Derbyshire. 



37. Avicula Bkamburiensis. — The Brambury Avicula, 

 pi. LXVI.** fig. 33. 



A. Bramhuriensis. Phillips, Geo. York, I. pi. 6, fig. 6. 



Ovate, slightly oblique ; hinge-line oblique, auricles a little 

 unequal ; surface with many longitudinal, divergent ribs, 

 which are furnished with numerous imbricated scales ; basal 

 margin a little scolloped; beaks obtuse, extending a trifle 

 beyond the hinge -line. 



The Great Oolite, Cloughton and Brora. 



38. Avicula Modiolaris. — The Modiola-like Avicula, 

 pi. LXI.** figs. 23, 24. 



A. modiolaris. Sowerby, Geo.Tr. 2d Ser. V. pi. 39, fig. IS. 



Obliquely and transversely elongated ; compressed ; keeled 

 towards the beaks; auricles undefined; hiuge-line straight. 



The Coal Measures, Coalbrook Dale. 



39 Avicula quadrata. — The Squarish Avicula pi. 

 LXI.** 27, 28. 



