208 NEW YORK STATE MUSEUM 



PLATE a 



(All ori^'luals in state museum) 



Rafinesquina alternata Emmons sp. 

 p. 16 



Fig. 



1 One of the specimens of large size and strong cardinal exten- 



sions occumng in pebbles of group 7. Natural size 



Christiania trentonensis sp. nov. 

 p. 21 



2 Pedicle valve, somewhat exfoliated, x 2 



3 Lateral view of same, x 2 



4 Brachial valve, x 2 



5 The interior of a brachial valve showing the quadruple adduc- 



tor scar divided by high, vertical, muscular walls, x 2 



6 Further enlargement of the cardinal region of the same show- 



ing the bilobed cardinal process and the denticulations on 

 either side of the latter 

 Pebbles of group 5 



Liospira americana Billings sp. 



p. 31 



7 Section natural size 



Pebble of group 5 



Cyrtospira attenuata sp. nov. 



p. 35 

 8 Dorsal view, x 2 



Pebble of group 7 



Eccyliopterus spiralis sp. nov. 

 p. 34 



9 Tapper side of specimen. Natural size 



10 T^ateral view of same showing a portion of the collarlike upper 

 carina. Natural size 

 Pebbles of gr-oup 5 



