452 EXPLANATION OF PLATES. 



59,60. Syntrielasma hemiplicata, Hall. Carb. ; Ills., . 332 

 61, 62. ProductusgiganteuSjSowb. ^. Carb. Limest.; Eng., 832 

 63-65. Procluctus horridus, J. Sowb. Zechstein, Gera, . 332 



66. Strophalosia excavata, Geinitz. Palaeozoic; Europe, 333 



67, 68. Strophalosia (Aulosteges) Wangeuheimi, de Yern. 



Permian ; Russia, ....... 333 



69-71. Chonetes striatella, Dalm. U. Silur. ; Europe, . 333 

 72-75. Crania anomala, Miiller. f. Zetland. 7^, ventral 

 valve; 75, dorsal valve; 7^, ditto, with animal, the 

 mantle removed ; a, anterior adductors ; a', posterior 

 adductors ; c, posterior adjusters ; c', cardinal 

 muscle ; r, o, central and external adjusters, . . 335 

 76,77. Crania (Cgraniscus) velata, Quenst. TJ. Jurassic; 



Oerlingerthal, ........ 335 



78-80. Crania (Ancistrocrania) Parisiensis, Defr. Upper 



Cretaceous ; France, . . . . ... . 335 



81, 82. Monomerella prisca, Billings. U. Silur. ; Ontario, 



Canada, ......... 336 



Plate 140. 



83, 84. Diuobolus Conradl, Hall. Niagara Limestone ; 



Leclaire, Iowa, ........ 336 



85-87. Trimerella Lindstromi, Dalm. II. Silur. ; Gotland, 336 



88-93. Discina (Dicinisca) lamellosa, Brod. Recent ; Peru. 

 91. dorsal valve ; 92, ventral lobe ; 93, the animal as 

 seen on the removal of part of the lower mantle-lobe ; 

 the extremities of the labial arms are displaced for- 

 wards, in order to show their spiral terminations ; p 

 is the expanded surface of the pedicle ; the mouth is 

 concealed by the overhanging cirri. The mantle- 

 fringe is not represented, m, umbo ; /, foramen ; d, 

 disk ; a, anterior adductors ; a', posterior adductors; 

 e, c', central and posterior adjusters ; r, external 

 adjusters, ......... 338 



94. 95. Obolus Davidsoni, Salter. Wenlock Limestone ; 



Dudley, 338 



96-98. Trematis terminalis, Emmons. Silur. ; Europe, 



N. America, . . . . . . • . 340 



99, 100. Obolella chromatica, Billings. L. Silur. ; Canada, 339 

 1.2. Kutorgina cingulata, Billings. Silur.; Canada, . 339 

 3. 4. Leptobolus lepis. Hall. Hudson River Gr. ; Cincin- 

 nati, Ohio, 339 



5. Schizoci-auia filosa, Hall. L. Silur. ; Ohio, . . . 340 

 6-8. Siphouotreta verrucosa, Yerneuil. Silur. ; Europe, . 340 

 9.10 Acrotreta subconica, Kutorga. Silur.; Europe, . 341 



