BRACHIGPODA—PROTREMATA, 



279 



Fig. 339. 



Gypidula p±eudogalea1a (Pal. 

 N. Y.). 



vated into a more or less distinct mesial fold. Brachial valve de- 

 pressed anteriorly into a sinus. Surface usually bearing below a 

 few rounded plications which 

 become obsolete above, leav- 

 ing the upper part of the valve 

 marked only by concentric 

 striae. 



Illinois, Iowa, Nevada, 

 Manitoba. 



236. G. romingeri Hall and 



Clarke. (Fig. 340.) 



Devonic. 

 Large. Pedicle valve very 

 convex ; brachial valve de- 

 pressed convex. Surface covered with strong plications which 

 frequently bifurcate irregularly toward the front. 



Hamilton of Michigan. 



LXXI. Amphigenia Hall. 



Elongate- ovate, high-shouldered, 

 without median fold or sinus. Pedi- 

 cle valve with a spondylium, bra- 

 chial valve with a large hinge plate 

 perforated at the apex by a fora- 

 men. Surface marked by concen- 

 tric growth lines and faint radial 

 striae. Devonic. 



237. A. elongata (Vanuxem). 



(Fig. 341.) Devonic. 



More or less gibbous, with 

 broadly rounded front. Pedicle 

 valve the more convex ; beak 

 closely incurved over the umbo of 

 opposite valve. Both valves often 

 abruptly elevated above the middle. 

 Shell structure punctate. 



Oriskany and Onondaga of New 



*' i \ i 



Fig. 340. Gypidula romingeri, ex- 

 ternal view and interior of brachial 

 valve. (After Hall and Clarke.) 



York, Michigan, Ontario, etc. 



