Fig. 



43 & 46. Thecidium Deslongchampsii. Interior of dorsal valve and profile, to shew the surface of attach- 

 ment, /. 

 44. ,, smwa^a, E. Desl. Exterior, /, point of attachment. 



4;"). ,, „ Interior of dorsal valve. 



47. „ Moorei. Profile to shew the extent of attachment in this species,/. 



48. SpiRiFEii STRIATUS, Martin, sp. Type of the genus. Interior of dorsal valve, shewing the internal 



spires, from a specimen in the Cambridge Museum. 



49. „ „ Interior of ventral or dental valve, from a specimen in the British 



Museum. 



50. „ Lonsdalii. Interior of dorsal or socket valve, from a specimen in the British Museum. 



51. ,, speciosus. Viewed from the beaks, to shew the double areas and pseudo-deltidium. 



52. „ Mosquensis. Interior oi ventral or dental valve, type of Fischer's genus Choristites. 



53. „ CyrtcBua. Iwtmov o^ ventral valve. 



54. ,, Verneuilii, = genus Trigonotreta, Kcenig- 



55. „ Paillettii. To show the large development of the mesial fold in this species. 



56. ,, cheiropteryx. 



57. ,, glaber. Type of M'Coy's genus Martinia. 



58. „ reticulatus ^ genus Reticularia, M'Coy. 



59. ,, hemisphcericus =: genus Br achy thy ris, M'Coy. 



60. Spiriferina rostrata. Interior of ventral or dental valve ; type of D'Orbigny's genus Spiriferina. 



61. Cyrtia trapezoidalis. Type of Dalman's genus C?/>'^i« ; f, foramen. 



62. ,, „ A fragment of the area and deltidium, to shew that at a certain age the 



foramen is closed ; in a species from Belgium and China (C. Murchisoni), 

 the circular foramen exhibits a tubular expansion, as seen in some Rhyn- 

 chonellce, such as R. octoplicata, &c. 



63. Cyrtia? heteroclyta. Exterior. 



64. ,, ,, Iwimov oi ventral OY dental valve. 



65. Spibigera concentrica. Exterior. 



66. „ ,, Interior of dorsal valve, showing the largely developed hinge plates, 



and four pits for the insertion of the pedicle muscles ; n' visceral I 

 foramen, communicating with the tube. 

 67- „ ,, Interior of ventral valve. 



68. „ ^ec^i«i/era = genus Cte'oMym, King (not Phillips) . 



69. ,, plano-sulcata = genus Actinoconchus, M'Coy, exhibiting the largely developed marginal 



expansions. 



70. „ phalaena, Phil., sp. = Hispanica, Vern. 



71. Athyris TUMiDA. Interior of vcntral valve. 



72. ,, ,, Fragment of the interior of dorsal valve, to show the mesial septum not occur- 



ring in Spirigera. 



73. „ Herculea, Barrande, sp. 



74. ,, ,, Specimen in which a small portion of the beak and umbo has been removed to 



exhibit the shoe-lifter shaped process, e', on which repose the dental 

 plates, X ; s, septum in dorsal valve. 



75. „ ,, A specimen seen from the beaks, in which a portion of tiie shell has been 



removed, so as to exhibit the shoe-lifter process, e', and dental plates, x. 



76. ,, ,, Section of both valves to shew the largely developed dental plates in the 



ventral valve, and septum in the dorsal one. Fig. 74, 75, and 76, were 

 kindly communicated to me by my friend Mr. Suess, of Vienna. 



77- Retzia Adrieni, Vern., sp., type of Professor King's genus Retzia. 



78. Spirigera? mucronata, Vern., sp. D, deltidium. 



