206 

 (Ii.m 8 STROPHALOSIA. King. 



[lvrv. : 8trophe, bending: <//«*. a disk.] 



L844. Annals and Magazine of Natural History, Vol. XIV., p. 313. 

 1892: Pal. X. Y.. Vol. VIII.. Pt. I., p. 314) 



Shell similarin Form to Productella. Ahingearea ispresent 

 in each v r alve,and the central opening is in each case covered 

 by ;i plate; ;i scar or cicatrix marks the former place of 

 attachment. Dental lamellae are absent. The cardinal pro- 

 cess of the brachial valve is erect, bifid on its anterior face 

 and quadrifid on its posterior face, continued in front in a 

 septum which extends for half the length of the shell, and 

 supported on each side by short, arched crural plates. The 

 surface of the pedicle valve is covered with spines, that of the 

 brachial valve either spinous, lamellose, or smooth. 



Strophalosia truncata. (Hall.) (Fig. 113.) (Pal. 

 X. V.. Vol. IV.. ].. 160, Productella truncata.) 



Distinguishing Characters. — Small size: gibbous ami 

 regularly arched pedicle valve, which is broadly truncated 







Fig. 113. 8trophnlosia truncata. Ventral valve, with beat slightly truncated ; ventral, 

 cardinal and profile views of a small specimen, from limestones of the Marcellus shales, 

 x 8 : four Interiors "f brachial valves, natural size, enlarged, x 2. much enlarged (portion 

 only), and natural size (from Hall). 



mi the umbo: flattened auriculate cardinal extremities: 

 minutely truncate, gently concave brachial valve: wrinkled 

 cardinal margins, and scattered surface spines. 



Found in the Nautilus bed on the Lake Shore (rare); 

 Strophalosia bed on the Lake Shore (extremely abundant): 

 Marcellus shale, in Bay View Cliff (rare). 



