130 



MOLLUSCA. 



Ateypa. 



Plentiful in the Devonian Limestone at Petherwin. 



26. Atrypa indentata. — The Indented Atrypa, pi. LIV. 

 fig. 23, 24. 



Atrypa indentata. Sowerby, Geo. Trans. V. 2nd series, pi. 



54, fig. 6. 



Transversely obovate, with an indented base; beak small, and 

 produced ; edge of the lower valve elevated. 



Devonian Limestone, Petherwin and Barnstaple, where it is 

 very abundant. 



27. Atrypa juvenis. — The Young Atrypa, pi. LIV. fig. 

 74, 75. 



Atrypa juvenis. Sowerby, Geo. Trans. V. 2nd series, pi. 56, 

 fig. 8. Phillips, Pal. Fos. p. 90, pi. 35, fig. 165. 



Longitudinally ovate, slightly convex, smooth, curved ; base 

 a little pointed ; valves nearly equal, the lower curved upwards, 

 with a small beak. 



Devonian Limestone, Plymouth. 



28. Atrypa lachryma — The Tear Atrypa, pi. LIV. fig. 

 30, 31. 



Atrypa lachryma. Sowerby, Geo. Trans. V. 2nd series, pi. 



56, fig. 9. 



Longitudinally subglobose, smooth ; beak hardly prominent ; 

 sides rounded, and nearly equal ; base straight, or slightly waved, 

 scarcely raised, except at the edge, which is deeply sinuated by 

 the projection of the inferior valve ; mesial furrow broad, flat, 

 and bounded by two sharp ridges. 



Devonian Limestone, Plymouth. 



29. Atrypa stbiatula. — The Finely-striated Atrypa, pi. 

 LIV. fig. 46. 



Atrypa striatula. Sowerby, Geo. Trans. V. 2nd series, pi. 

 54, fig. 10. 



Suborbicular, convex ; surface with fine, close-set, longitudi- 

 nal, divergent striae. 



Devonian Limestone, Petherwin, Barnstaple, and Fowey. 



30. Atrypa plebeia The Common Atrypa, pi. LIV. 



fig. 51, 52. 



Atrypa plebeia. Sowerby, Geo. Trans. V. 2nd series, pi. 56, 

 fig. 12, 13. Spirifera plebeia, Phillips, Pal. Fos. p. 70, pi. 28, 

 fig. 121. 



Transversely obovate, smooth, and but slightly convex ; beak 

 hardly protruding ; base produced, and but little turned up ; 

 lower valve with a very slight depression. 



Devonian Limestone, Mount Wise, Plymouth, and Barton. 



31. Atrypa spheric a. — The Spherical Atrypa, pi. LIV. 

 fig. 57, 58. 



Atrypa spharica. Sowerby, Geo. Trans. V. 2nd series, pi. 



57, fig. 3. 



Ventricose, nearly spherical, slightly wider than long ; beak 

 small, adpressed; surface with large, longitudinal, rounded ridges, 

 and shallow intervening furrows; base deeply sinuated, with five 

 elevated ribs. 



Devonian Limestone, Plymouth. 



32. Atrypa hemisph^rica. — The Hemispherical Atrypa, 

 pi. LIV. fig. 14, 15. 



Atrypa hemisphcerica. Sowerby, Sil. Syst. p. 637, pi. 20, 

 fig. 7. 



Nearly orbicular, fan-shaped ; valves unequal, the one hemis- 

 pherical, the other almost flat ; with a nearly straight back, and 

 about twelve angular radii. Length four lines ; breadth five lines. 



Lower Silurian Rocks, Ansterdine Hill ; Worcestershire ; 

 Damory Hill, Michaelwood Chace, Gloucestershire. 



33. Atrypa latissima. — The Very Broad Atrypa, pi. 

 LIV. fig. 16, 17. 



Atrypa latissima. Sowerby, Geo. Trans. V. 2nd series, pi. 

 56, fig. 25. 



Transversely oblong-ovate ; beak short, and nearly straight ; 

 one valve gradually rounded, the other with the centre of the 

 base suddenly reflected, and slightly hollowed, with a corres- 

 ponding ridge in the other ; a series of radiating ribs invest the 

 margins of the valves, producing a crenulated edge ; upper 

 portion of the valves smooth, with a few lines of growth. 



Devonian Shales, Plymouth. 



34. Atrypa globosa. — The Globular Atrypa, pi. LIV. 

 fig. 25, 26. 



Atrypa globosa. Sowerby, Sil. Syst. p. 637, pi. 22, fig. 2 6. 



Globular, smooth, with obscure channels. Diameter about 

 six lines. 



Lower Silurian Rocks, Castell Craig ; Gwyddon ; and 

 Gorllwyn ; Caermarthenshire. 



35. Atrypa gibbera. — The Gibbous Atrypa, pi. LIV. 

 fig. 42, 43. 



Atrypa gibbosa. Portlock, Geo. Rep. p. 460, pi. 38, fig. 1 . 



General form nearly orbicular ; both valves convex, the ven- 

 tral one remarkably so, having a haunch-backed aspect, with a 

 faint mesial ridge, corresponding to the tongue in the other 

 valve ; dorsal valve depressed for nearly half its length, from 

 whence it suddenly descends, and contracts in the centre into a 

 small tongue-shaped process, which protrudes into the ventral 

 valve ; beaks distant ; when viewed through a lens the surface 

 presents a finely radiated appearance. 



Carboniferous Limestone, Tyrone, Ireland. 



36. Atrypa decussata. — The Decussated Atrypa, pi. 

 LIV. fig. 54. 



Atrypa decussata. Sowerby, Geo. Trans. V. 2nd series, pi. 

 54, fig. 5. Spirifera decussata, Phillips, Pal. Fos. p. 70, pi. 

 28, fig. 120,* b, c, d. 



Circular; both valves uniformly convex; beaks incurved, ap- 

 proximate ; whole surface with rather sharp, concentric striae, 

 and very fine, equal, interrupted, radiating hues, which give it a 

 slightly crenulated appearance. 



In some specimens every third or fourth of the concentric striae are 

 larger than the othei-s. 



Devonian Shales, Brushford ; Boggy Point ; Pilton ; and 

 Petherwin. 



37- Atrypa lineata The Lineated Atrypa, pi. LIV. 



fig. 60, 61. 



Terebratula lineata. Sowerby, IV. p. 39, pi. 334, fig. 1, 2. 

 Spirifera lineata, Phillips, Pal. Fos. p. 70, pi. 28, fig. 120, a. 

 Anomites lineatus, Martin, Pet. Derb. pi. 36, fig. 3. 



Transversely oval, gibbose ; umbones rather produced, in- 

 curved, and approaching, the intervening area with an angular 

 sinus; whole surface with transverse, rather distant sulci, and 

 very minute, close, longitudinal stria;. 



Carboniferous Limestone, Kirby Lonsdale ; Castleton, Der- 

 byshire ; South Petherwin ; and Ireland. 



38. Atrypa imbricata The Imbricated Atrypa, pi. 



LIV. fig. 66, 67. 



Terebratula imbricata. Sowerby, IV. p. 40, pi. 334, fig. 

 3, 4. Spirifer imbricata, Phillips, Geo. York. II. pi. 10, fig. 20. 



