122 



MOLLUSCA. 



Lept^na. 



Semielliptical, very convex; hinge line somewhat longer than 

 the width of the valves ; margin slightly deflected ; lower valve 

 greatly and regularly convex, the other nearly equally concave ; 

 the whole surface concentrically wrinkled, but almost obsolete 

 near the disk ; with adpressed spines, those contiguous to the 

 hinge line considerably elongated. 



Found in the Devonian Shales at Petherwin, Barnstaple, and 

 Croyde. 



3. Lept^na sordida. — The Dilapidated Leptaena, pi. 

 LIII.* fig. 19. 



Leptcena sordida. Sowerby, Geo. Trans. V. 2nd series, pi. 

 53, fig. 5 and 16. 



Transversely elongated, somewhat convex ; hinge line not 

 quite equal to the breadth of the valves, with rounded angles ; 

 surface irregularly striated ; muscular impressions occupying 

 nearly half the internal area. Variable in width, sometimes 

 almost orbicular, at others its width nearly double its length. 



Carboniferous Limestone, Tenby ; Devonian Limestone, 

 Linton and Torquay ; and the Upper Ludlow Rocks, West- 

 morland. 



4. Lept^na fragaria The Rough Leptsena, pi. LIV. 



fig. 9. 



Leptcena fragaria. Sowerby, Geo. Trans. V. 2nd series, 

 pi. 54, fig. 3, and pi. 56, fig. 5, 6. Phillips, Pal. Fos, p. 59, pi. 

 25, fig. 100. 



Nearly hemispherical, with the sides slightly produced; beak 

 of the convex valve subacute; hinge line somewhat shorter than 

 the width of the valves; surface concentrically undulated, almost 

 smooth, and pustulated. 



Found in the Devonian Shales at Plymouth and Petherwin. 



5. Lept^na rugosa The Rugged Leptaena, pi. LIV. 



fig. 36. 



Leptcena rugosa. Sowerby, Geo. Trans. V. 2nd series, pi. 

 56, fig. 4. Phillips, Pal. Fos. p. 57, pi. 24, fig. 95. 



Semicircular ; hinge line prolonged into two short, auriform 

 processes; lower valve a little convex, and bent upwards on the 

 edge to meet the upper valve ; surface with regular, concentric 

 wrinkles; border provided with rounded undulations, crossed by 

 numerous, equal, straight, filiform stria?. Length one inch. 



Found in the Devonian Shales at Plymouth and Newton 

 Bushel ; and in the Lower Silurian Rocks at Coniston. 



6. LEPTiENA PRiELONGA — The Lengthened Leptaena, pi. 

 LIIL fig. 62, 63. 



Leptaina prcelonga. Sowerby, Geo. Trans. V. 2nd series, 

 pi. 53, fig. 29. 



Transversely obovate, convex, with a central furrow; beak of 

 larger valve ventricose, and overhanging that of the smaller one, 

 which is concave ; margin considerably deflected ; hinge line 

 shorter than the width of the shell, from which emanate a few 

 concentric undulations; whole surface with coarse, irreuular, 

 transverse stria;. 



Found in the Devonian Shales at Croyde Bay. 



7. Lept^na reticulatus — The Reticulated Leptaena, 

 pi. LIIL fig. 53, 54. 



Spirifera? crenistria. Sowerby, Geo. Trans. V. 2nd series, 

 pi. 57, fig. 7. 



Subovate, subcompressed ; hinge line parallel, extending the 

 entire breadth of the valves; sides nearly straight; base round- 

 ed ; whole surface covered with strong, divergent striae, and 



crossed by concentric, less decided striae, giving it a finely 

 reticulated aspect. 



Mountain Limestone, Matlock, Derbyshire. 



8. Lept^na Lepisma The Silvery Lepta;na, pi. LIIL* 



fig. 25. 



Leptcena Lepisma. Sowerby, Sil. Syst. p. 618, pi. 8, fig. 7- 



Semicircular, convex, with a shining, silvery, or satin-like 

 lustre ; surface with a few obscure, slightly elevated, forked 

 radiations, and indistinctly punctated ; hinge line as wide as the 

 shell ; base moderately deflected. Length nearly three lines ; 

 breadth five lines and a half. 



Lower Ludlow Rock, near Clangunford. 



9- Lept/ena euglypha The Well-carved LeptEena, pi. 



LIII. fig. 28. 



Leptcena euglypha. Dalman, Act. Holm. 1827, p. 118, pi. 

 I , fig. 3. lb. Hist. Pet. Suec. pi. 20, fig. 4. Sowerby, Sil. Syst. 

 p. 618 and 623, pi. 12, fig. 1. Orthis euglypha, Von Buch. 



Subtriangular ; base obtuse ; flat above ; hinge area long, 

 straight, and narrow; surface covered with numerous, radiating, 

 slender ridges, with intermediate, fine, elevated striap. Length 

 of flat space one inch; width two inches and a half; depth in 

 front at base one inch. 



This species is liable to considerable variation in form : the sides in 

 some specimens being considerably less flattened than in our figure ; the 

 intermediate striae sometimes as large as the ridges ; and the sides at the 

 hinge line shooting out to extended angles ; the striae are also frerjuently 

 like those of Orthis alternata. 



Wenlock Limestone at Aston, near May Hill, Daley; Fawn- 

 hope ; Abberley and Wigmore. 



10. Lepttena depressa The Depressed Leptaena, pi. 



LIII.* fig. 29, 30, 31. 



Leptcena depressa. Dalman, 1. c. p. 106, pi. 1, fig. 2. lb. 

 Hist. Pet. Suec. p. 69, pi. 20, fig. 3. Sowerby, Sil. Syst. p. 

 623, pi. 12, fig. 2. Producta depressa, Sowerby, Min. Conch. 

 V. pi. 459, fig. 3. 



Nearly semicircular, depressed above, with strong, longitudi- 

 nal striae, which are interrupted by transverse, wide-set, narrow 

 furrows; hinge area long, with the sides extended into auriform 

 processes ; upper valve with a rounded and somewhat produced 

 umbo, and concave near the margin ; front or basal margin 

 abruptly curved, deflected, and descending info a very broad 

 space, which in depth is equal to the length of the shell ; lower 

 valve concave in the centre. Length of flat portion about 

 three-quarters of an inch; width one inch and a half; deflection 

 one inch. 



This species must not be confounded with L. analorja, to which it is 

 very nearly allied. The outline of the latter approaches nearer to a 

 semicircle, and it is usually larger than the L. depressa. 



Very common in the Amestry and Wenlock Limestones ; 

 and is also met with, although sparingly, in the Mountain 

 Limestone. 



Its localities are Dudley, Wenlock ; Amestry, May Hill ; 

 Abberley and Stourbridge. 



11. LeptjEna papilionacea. — The Butterfly-like Lep- 

 taena, pi. LII. fig. 24. 



Spirifera papilionacea. Phillips, II. p. 221, pi. 11, fig. 6. 



Extremely wide, almost semielliptical; hinge line parallel; 

 umbones very small ; surface covered with very fine, longitudi- 

 nal, bent, divergent strice ; crenulated in the young state. 



Mountain Limestone, Bolland, Otterburn, and Kendal. 



