Avin.LA. 



CONCH IFERA. 



161 



IJ. AviccLA RETICULATA. — The Roticulatcil Avicula, pi. 

 LXVI.* fig. 20. 



A. reticii/afa. Soworby, Sil. Syst. pt. II. p. Gil', pi. C, fig. 3. 



Oblong ovate, obliiiuc, one valve ratlier convex, anil the 

 dtlior nearly flat ; both pointed towards the beaks, and broad 

 at the base ; surface with uumerous, longitudinal, divergent 

 ribs, decussated by rather strong lines of growth ; auricles un- 

 equal ; one hardly developed, the other very large and rectan- 

 gular. 



Aymestry Limestone, Croft Valley, Aymestry ; Lower 

 Ludlow, Jlyddleton Hall, Wenlock Limestone, Falfield and 

 Totworth. 



16. Avici'LA ORBICULARIS. — The Orbicular Avicula, pi. 

 LXVI* fig. 21. 



A. orbicularis. Sowerby, Sil. Syst. pt. II. p. C35, pi. 10, fig. 2. 



Nearly orbicular, convex, and almost smooth ; with a few 

 almost obsolete lines of growth ; beaks produced ; auricles 

 small, the anterior one round, the posterior not protrudiug be- 

 yond the margin ; hinge-line straight ; length and breadth 

 nearly equal. 



The Caradoc Sandstone, Acton Scott, near Caradoc ; 

 Honderly and Cheney Longville. 



IT. AviccLA MuRCHisoNi. — Murchison's Avicula, pi. 

 LXVI.* fig. IS. 



A. orhicularis. Sowerby, Sil. Syst. pt. II. p. 635, pi. 20, 

 fig. .3. 



Obliquely elongated, rather inflated, smooth, or with nearly 

 obsolete lines of growth, and very obtuse, imperfectly deve- 

 loped, concentric ridges ; beaks small, acute ; anterior auricle 

 very small, its outline undulous ; posterior auricle not pro- 

 truding beyond the margin ; with a very slight obtuse flexure 

 beneath it. 



The Caradoc Sandstone, Acton Scott. 



18. AviciLA RECTANGULARis. — The Rectangular Avicula, 

 pi. LXVI.* fig. n. 



A. rec/anfftdaris. Sowerby, Sil. Syst. pt. II. p. 603, pi. 3, f. 2. 



Smooth, obliquely sub-triangular, and very convex ; hinge- 

 line long, straight ; anterior side almost straight ; posterior 

 side produced, in the form of a lobe ; front rounded ; beaks 

 rather acute and slightly turned downwards ; auricles not de- 

 fined. 



The Old Reil Sandstone, Iloreb Chapel, in the Cwm-dwr, 

 between Trccastle and Llandovery, Wales. 



19. AvicDLA HCMATA. — The Buried Avicula, pi. LXVI.** 

 fig. 1. 



A. ohliqua. Brown, Trans. Manch. Geo. Soc. I. p. 225, pi. 7, 

 fig. 64. 



Sub-depressed, valves very oblique ; hinge-line long, nearly 

 straight ; surface with numerous elevated, divergent, longitu- 

 dinal ribs, emanating from the slightly protruding beaks, and 

 terminating a little beyond the margin, producing a creuulated 

 edge, crossed l>y many fine lines of growth ; auricles of medium 

 size, the anterior one only defined ; length and breadth about 

 half an inch. 



The Coal Shale, Crimsworth and Vale of Todmorden. 



20. AvicrLA Samielsii. — Samuels' Avicula, pi. LXVI.** 

 fig. 29. 



A. SamueUii. Brown, Trans. Manch. Geo. Soc. I. p. 225, 

 pi. 7, fig. 65. 



Semicircular, wider than long , hinge-line straight ; the 

 auricles undefined ; beaks small, pointed, and not much pro- 

 duced beyond the hinge-line ; surface covered with rounded, 

 longitudinal, divergent ribs, which cmanato from the beaks 

 and pass over the margin, giving a fine pectinated appearance, 

 crossed by numerous distinct lines of growth. Length up- 

 wards of a quarter of an inch ; breadth, a third more. 



The Coal Shale, High-Green Wood, Valo of Todmorden. 

 Named in honour of my friend .John Samuels, Esq., of Barton 

 House, Jlanchester, Vice-President of the Manchester Na- 

 tural History Society. 



21. Avicula Bin^jeyi. — Binney's Avicula, pi. LXVI.** 

 figs. 5, 6. 



A. Binneyi. Brown. Trans. Manch. Geo. Soc. I. p. 65, 

 pi. 6, figs. 27, 28. 



Smooth, oblique, beaks prominent, acute ; larger auricle 

 nearly parallel with the hinge-line and undefined ; the other 

 small ; hinge-line straight ; posterior side abruptly contracted ; 

 interior side very broad; centre of the valves considerably 

 voutricoso. Length three-sixteenths of an inch ; breadth 

 nearly a quarter of an inch. 



The New Red Sandstone, Newtown, Lancashire. 



22. Avicula inflata. — The Inflated Avicula, pi. LXVI.** 

 figs. 4 and 8. 



A. inflata. Brown, Trans. Man. Geo. Soc. I. p- 65, pi. 6, 

 figs. 25, 26. 



Oblique, inflated, transversely oblong-ovate ; hinge placed 

 much to one side, where it is narrow and subcompressed, with 

 a small and acute auricle, widening rapidly towards the oppo- 

 site side. Length three-sixteenths of an inch, breadth a quar- 

 ter of an inch. 



The New Red Sandstone, Newtown, Lancashire. 



23. Avicula tenua. — The Thin Avicula, pi. LXVIII. 

 fig. 9. 



P. Brown, Trans. Man. Geo. Soc. I. pi. 5, fig. 23. 



Oblique, compressed ; hinge-line slightly oblique ; anterior 

 side nearly straight, with the auricle undefined ; posterior side 

 with a considerable curvature under the car, beneath which it 

 is produced and rounded ; surface smooth, with irregular in- 

 equidistant, concentric, slight wrinkles. 



In the Black Bass, Pendleton Coal Mine, near Slan- 

 chester. 



24. Avicula squamula. — The Scale Avicula, pi. 

 LXVIII. fig. 10. 



Oblique, compressed ; hinge-line slightly oblique ; anterior 

 side nearly straight ; posterior side very slightly curved ; 



few 



solete concentric 



surface smooth, with a 

 wrinkles. 



The CoaJ Shale, XaXo of Todmorden, 



25. Avicula ano.mala. — The Anomalous Avicula, pi. 

 LXVI.* fig. 22. 



A. anomala. Sowerby, Geo. Tr. 2d Ser. IV. p. 342, pi. 17, 

 fig. 18. 



Very obliquely elongated, imperf^tly five angled, disk 

 flattened ; beaks acute, protruding beyond the hinge-line, 

 which is greatly obliqued ; surface with many longitudinal 

 narrow elevated ridges, crossed by slightly defined lines of 

 growth ; valves very deep, together measuring about one and a 

 half inch, with a square section ; basal line sub-triangular. 



The Greensand, Blackdown. 



2p 



