PLATE LXXIII. 



(Figures 1-10, lt-19 by E. EMMONS ; II by G. B. Simpson ; 12, 13, 20 by E. P. Whitmkld.) 



Genus STRICKLANDINIA, Billings. 



Page 249. 



Stricklandinia multilirata, Whitfield. 



Pigs. 1,2. Ventral and dorsal views of an inti-rnal silicious cast. The iigures show the short, straight 

 hing-e, the sharp delimitation of the cardinal region and the orbicular outline of the valves. In 

 figure 1 is seen the low median groove and the apex of the tilling of the spondylium ; figure 2 

 shows the median fold of the brachial valve and the cast of the small but prominent muscular 

 scar. 



Niagara dolomites. Near Milwaukee, Michigan. 



Stricklandinia castellana, White. 



Figs. 3-6. Doreal, profile, cardinal and ventral views of a characteristic specimen ; showing the nearly 

 equiconvex valves, the strong, irregularly fasciculate or duplicate 'plication, and, in fig. 5, the 

 cavities left by the spondylium and low median septum of the pedicle-valve. 



Fig. 7. Cardinal view of a partial internal cast, the pedicle-valve being represented beneath ; showing 

 the position of the spondylium and its supporting septum and the casts of the muscular im- 

 pressions on the brachial valve. 



Niagara group. Jones county, Iowa. 



Stricklandinia drformis, Meeiv und Worthen. 



Figs. 8, 9. Profile and cardinal views of an internal cast ; showing the delimitation of the cardinal area of 



the pedicle-valve and the filling of the spondylium. 

 Fig. 10. Dorsal view of the umbonal portion of a specimen, to show the short, stiaight hinge-line and the 



subauriculate cardinal extremities. 



Niagara group. /Si. Charles, Illinois. 



Stricklandinia Gaspensis, Billings. 



Fig. 11. Dorsal view of a large individual, drawn from a plaster cast of the original specimen; showing 

 the form of the shell, a portion of the cardinal area and the abundant plication of the surface. 

 Uppei- Silurian. Oaspi, Nova Scotia. 



Stricklandinia Anticostiensis, Billings. 



Fig. 12. The interior of the umbcmal portion of a brachial valve ; showing the short, convergent crural 

 plates and the low median muscular ridge in the bottom of the valve. 



Fig. 13. A view looking into the umbonal cavity of the pedicle-valve ; showing the spondylium and its 

 supporting septum. 



Fig. 14. The interior of a pedicle-valve, distorted by natui al growth, and showing a sharply defined car- 

 dinal area, delthyrium and spondylium. 



Stricklandinia Davidsoni, Billings. 



Fig. 15. Dorsal view of an average example ; showing its trilobed, medially elongate form. 

 Anticosti group. Anticosti. 



