160 



CONCHIFERA. 



AviCL'LA. 



The Coal Measures, Bradford, Leeds, and Coalbrook Dale. 



2. AvicuLA OwENi. — Owen's Avicula, pi. LXV. fig. 13. 



Nearly orbicular, very much compressed, with large unequal 

 ears, which are destitute of striae ; surface with numerous, 

 rather close, divergent striie, and a few distant, distinct lines 

 of growth ; sides plain. 



Differs from the preceding in the valves being perfectly 

 straight. In the Museum of the Manchester Natural History 

 Society, and named in honour of its Secretary. 



The Coal Measures, Vale of Todmorden. 



3. Avicula simili. — The Similar Avicula, pi. LXV. fig. 

 12. 



Nearly orbicular ; ears very large, with transverse oblique 

 radiated strife, and longitudinal, nearly obsolete ones ; hinge- 

 line a little triangular ; surface smooth, with divergent striae, 

 and remote indistinct lines of growth, one side with the ear 

 and margin straight. 



The Coal Measures, Vale of Todmorden. 



4. AvicDLA PLiCATA. — The Plicated Avicula, pL LXV. 

 fig. S. 



Nearly orbicular ; somewhat oblique ; the valves much com- 

 pressed ; hinge-line somewhat triangular ; ears large, unequal, 

 with divergent, transverse, distinct stria;, crossed by wider 

 curved strise ; one ear concave on the side ; whole surface with 

 numerous radiating stris, crossed by remote, indistinct ones ; 

 margins even. 



The Coal Measures, Middleton, near Leeds. 



5. Avicula nEiiispii.EEicA. — The Hemispherical Avicula, 

 pi. LXV. fig. 5. 



Pecten /tcmisphwrica. Phillips, Geo. York, II. p. 212, 

 pi. 6, fig. 16. 



Nearly orbicular ; the lower valve circular and very con- 

 vex, with the sides gradually passing into the undefined ears ; 

 hinge-line straight and a little oblique ; surface with squa- 

 luose stria;. 



The Cai'boniferous Limestone, Bolland. 



6. Avicula ketroflexa. — The Bent-back Avicula, pi. 

 LXVL' fig. 17. 



A. retro/iexa. Sowerby, Sil. Syst. II. p. 609, pi. 5, fig. 9. 



Short, very broad, semicircular, oblique, somewhat convex, 

 transversely wrinkled; anterior ear very small, length 10 

 lines, breadth if inch. 



The Upper Ludlow Rock, Hale-end, Melverns, near L^sk. 



7. Avicula costata. — The Ribbed Avicula, pi. LXVL* 

 figs. 7, 8, 9. 



A. eostata. Sowerby, III. p. 77, pi. 244., fig. 1. 



Deeper valve transversely ovate ; auricles nearly equal ; 

 surface with eight smooth, longitudinal, curved, divergent 

 ribs, with internal furrows corresponding to the external ribs, 

 which project beyond the margin ; shallow valve nearly flat, 

 with numerous external rays, the posterior auricle of which 

 is separated from the shell by a deep narrow sinus, and pro- 

 vided with a few sharp teeth on the sides under the auricle, 

 the opposite auricle large, much elongated and acute, extend- 

 ing considerably beyond the body of the shell. 



The Cornbrash, Stoney Stratford. 



8. Avicula ix.equivalvis. — The Unequal-valved Avicula, 

 pi. LXVL* figs. 5, 6. 



..4. ina-quiraleis. Sowerby, III. p. 78, pi. 244, fig. 2- 



Deeper valve obliquely elliptical, convex, enveloping the 

 smaller valve, and furnished with a large projecting auricle, 

 which is a little rounded at the point ; surface with thir- 

 teen narrow, divergent, rounded ribs, projecting beyond the 

 margin, and striated in the interstices ; flatter valve a little 

 convex, smooth, with divergent furrows ; posterior auricles 

 of both valves very small ; substance of the shell extremely 

 thin. 



There are two varieties of this fossil, the one with strong 

 and the other with slender strire. 



The Kelloways Rock, Kelloways ; the Inferior Oolite, 

 Dursley and Blue Wick ; and the Lias in many localities. 



9. Avicula obliqua. — The Oblique Avicula, pi. LXVL* 

 fig. 23. 



A. obliqua. Sowerby, Sil.Syst.pt. II., p. 635, pi. 20, fig. 4. 



Elongated, obliquely ovate, conyex, smooth ; hinge-line 

 rather short, auricles undefined. Length 1 f inch. 



This species occurs in clusters in the Caradoc Sandstone, 

 Soudley, near Acton Scott, east flank of Ciier Caradoc. 



10. Avicula echinata. — The Spinous Avicula, pi. 

 LXVL** figs. 9, 10, 11. 



A. echinata. Sowerby, III. p. 75, pi. 243. 



Obovate, gibbose, a little longer than wide, deeper valve 

 with numerous muricated ribs, and unequal auricles, the ante- 

 rior one is nearly rectangular ; flatter valve generally wider 

 than long, smooth, with the anterior auricle acute. 



The Cornbrash, Atford, and Chippenham, the Great 

 Oolite, Bath, and the Lias, Yorkshire. 



11. Avicula lanceolata. — The ' Lanceolate Avicula, pi. 

 LXIX. fig. ,3. 



A. lanceolata. Sowerby, VI. p. 17, pi. 512, fig. 1. 



Extremely lengthened transversely, very flat ; obliquely 

 linear, lanceolate, and compressed ; its width about six times 

 its length ; posterior auricle large and obtusely angled, extend- 

 ino- to about one-third the breadth of the shell ; the anterior 

 auricle minute and pointed ; beaks placed near the anterior 

 extremity. 



The Lias, Lyme Regis, Dorsetshire. 



12. Avicula ovata. — The Ovate Avicula, pi. LXVL** 

 fig. 18. 



A. ovata. Sowerby, VI. p. 18, pi. 512, fig. 2. 



Convex, transversely ovate ; posterior side elongated and 

 obtuse; hinge-line long, occupying more than half of the shell, 

 forming part of the posterior wing, which is somewhat obscure. 



The Great Oolite, Stonesfield. 



13. Avicula media. — The Medium Avicula, pi. 

 LXXXIII. figs. 19, 20. 



A. media. Sowerby, I. p. 13, pi. 2. 



Ovate, compressed ; auricles large, unequal, one large and 

 acute ; hinge-line lengthened and parallel ; surface smooth. 

 The London Clay, Highgateand Sheppy. 



14. Avicula lineata. — The Lineated Avicula, pi. LXVL* 

 fig. 10. 



A. lineata. Sowerby, Sil. Syst. pt. II. p. 610, pi. 5, fig. 10. 



Obliquely ovate, compressed, surface with many radiating 

 elevated lines ; anterior auricle minute, posterior one well 

 marked, triangular, half as long as the posterior side. Length 

 nine lines ; width one inch and two lines. 



The Upper Ludlow Rock, near Ludlow. 



