PLATE LXXIII. 



(Kisures l-lii, H-['.> by E. Kmmdxs ; II liy (i. 1!. Simpson ; 12, l:i, iu by It. P. WiiiTFiKLU.) 



Gknus STRICKLANDINIA, Hillings. 

 Stricklandixia multilikata, Wliittield. 



Fi^s. 1, 2. Ventijil ami iloisiil views of an inti-rnal silii-ious cast. The Hjjures show the hIioH, straight 

 hing-e, the sharj) delimitation of the cardinal I'egion 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, Wliite. 



Figs. 3-G. Doi-sal, profile, cardinal and vcmtral \ie\vs of a characteristic specimen ; showing the nearly 

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

 cavities left i)y the spondylium and low median septum of the pedicle-valve. 



Fig. 7. Cai-dinal 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, lima. 



StkicklaiNdima dkformis, Mcuk mill W'oriluii. 



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, straight hinge-line and the 



subauriculate cardinal extremities. 



Niagara group, A'i. Charles, Illinois. 



Stricklan'ijinia Gaspensis, Uilliiig.s. 



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

 the form of the shell, a jjortion of the car<linal area and the abundant plication of the surface. 

 Upper Silurian. (}a.-ipe, Nova i<cotia. 



Stricklandinia Anticostiensis, Billings. 



Fig. 12. The interior of the umbonal 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 

 suppoi'ting se.ptiun. 



Fig. 14. The interior of a j)edicle-valve, distorted by natuial growth, and .showing a sharply defined car- 

 dinal area, delthyriuin and spondylium. 



Stricklandinia Davidsoni, Billings. 



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

 Anticosti group. Anticosti. 



