PLATE LXII. 



(Figures 1-5, 8-10, 14-16, •21-23, 37-45, 52. 53 by E. Emmons ; 7, S, 11-13, 17-20, -24-: ;, 4(!-51 by G. 11. Simpson.) 



Genus SYNTROPHIA, gen. nov. 



Page 21B. 



Syntrophia lateralis, Whitfield. 



Fig. 1. The exterior of a pedicle-valve ; showing the long, .straight hinge knd broad median sinus. 



Fig. 2. The exterior of a brachial valve ; showing the broad, obscure median fold. 



Fig. 3. The exterior of a small pedicle-valve. 



Fig. 4. A portion of the interior of the pedicle-valve ; showing the cardinal area and spondylium. X 3. 



Fig. 5. Cardinal view of conjoined valves which have been transvei-sely sectioned in the umbonal region ; 

 showing the spon<lylium in both valves. The shell has been cut just in front of the support- 

 ing septa, the brachial valve being above. X 2. 



Pig". 6. Cardinal view of the specimen represented in tig. 1 ; showing the cardinal area. 



Pigs. 7, 8. Internal casts of two brachial valves with impressions of vasculai- sinuses. 



Fig. 9. A portion of the interior of the pedicle-valve ; showing the comjilete spondylium and the division 

 of its surface into median (adductor) and lateral (diductor) mu.scular areas. X 3. 



Fig. 10. Oblique view of the specimen represented in fig. 1 ; showing the ele\ ation of the spondylium and 

 the length of its supporting median septum. 



Calciferous formation (Fort Casflin beds). Fort Cassin, Vermont. 



Genus CAMARELLA, Billings. 



Page 21H. 



Camarella Volborthi, Billings. 



Figs. 11, 12. Dorsal views of two shells ; showing a slight difference in outline and vei'y faint mfedian mar- 

 ginal plication. 



Trenton limestone. Jacksonburgh, N. Y 

 Pigrs. 13, 14, 15, 16. Profile, dorsal, ventral and front views of a more strongly plicated shell. X 2. 

 Pig. 17. Cardinal view of conjoined valves which have been transversely sectioned in the umbonal I'egion ; 



showing the spondylium of the pedicle- valve and its median supporting s(!ptimi. X 4. 

 Fig. 18. The interior of the umlxmal portion of the brachial valve ; .showing the small apical spondylium 

 and the median septum. X 4. 



Black River limestone. Patii/iiette'n liapids, Ottawa River. 



Camarella Panderi, Billings. 



Figs. 19, 20. Dosral and front views of an average example. 



Pigs. 21, 22, 23. Dorsal, front and profile views of an individual with no trace of lateral or marginal plica- 

 tions. X 2. 



Black River limestone. Pauquette's Mapids, Ottawa River. 



Genus SYNTROPHIA. gen. nov. 



Page 21(i 



Syntrophia (?) caloifera, Billings. 



Pig. 24. The exterior of the pedicle-valve; showing the elevated umbo, deep median sinus and extended 

 hinge-line. X 2. 



Quebec gi-oup. Pointe Levis, Canada. 



