PLATE LXXIV. 



(Kignres 1-9 by K. P. Whitfield.) 



Genus AMPHIGENIA, Hall. 



Page 262. 

 See Plate 73. 



Amphigenia elongata, Vanuxem. 



Vig. 1. Doraal view of a partial cast ; showinff the muscular impressions and vascular sinuses of the 

 brachial valve, and the cavity left by the medially divided hing«-plate. 

 Comifcrous limestone. Clarence, New Ym-k. 

 Fig. 2. Cardinal view of an internal ca.st : showing the filling of the spondylium and of the visceral fora- 

 men, and the cavities left by the median septum and hinge-plate. 

 Fig. 3. Median longitudinal seittion of both valves ; showing the degree of development of the spondy- 

 lium, median septum, and septal jtlates ; also the great thickness of the shell in the umbonal 

 region of the brachial valve and the length of the crura, with their convex terminal expansion. 

 Comiferous limestone. Le liay. New York. 

 Fig. 4. Dorsal view of an individual of medium size with regularly elliptical form and finely striated 



surface. 

 Fig. 6. An internal cast of the umbonal i>ortion of the brachial valve j showing the septal plates, the four 

 sharply defined scare of the adductor muscles, the va.<«;ular sinuses and genital markings. 

 Comiferous limestone. Westeiii New York. 

 Fig. 6. The exterior of a brachial valve having the characteristic subovate outline. 



Figs. 7, 9. Dorsal and profile views of a shell of full medium size with gibbous valves and finely striated 

 surface. 



Comiferous limestone. Cayuga, Ontario, 

 Fig. 8. Internal cast of a large brachial valve ; showing the muscular impi-ession and the cavity left by 

 the removal of the hinge-plate. 



Comiferous limestone. Le Roy, New York. 



