206 

 Gknis STROPHALOSIA. KiN(i. 



[Ety. : Strophe, bending; nlos, a disk.] 



(1844. Annals and Magazine of Natural History, Vol. XIV., p. 313. 

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



Sliell similai'iii form to Prodiictella. A hinge area is present 

 ill each valve, and the central opening is in each case covered 

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

 attachment. Dental lamella* are absent. The cardinal pro- 

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

 and qnadi-ifid on its pcjsterior face, continned in front in a 

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

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

 surface of the pedicle valve is covered with s]»ines,that of the 

 brachial valve either spinous, lamellose, or smooth. 



Stkophalosia TRixcATA. (Hall.) (Fig. 11*5.) (Pal. 

 N. y.. Vol. IV., p. 1(>0, rrodnrtf'Ihi truncat-i. ) 



IHstiuguishing Characters. — Small size: gibbous and 

 regularly arched pedicle valve, which is broadly truncated 



•'Sfe-f^'!^^ 



Fig. 113. Strophahjsia truncata. Ventral valve, with heak slightly truncated ; ventral, 

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

 X 3 ; four intei-iors of brachial valves, natural size, enlarged, x 2. much enlarged (portion 

 only), and natural size (from Hall). 



on the nmbo; 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). 



