PLATE XVIII. 

 Spurilla braziliana MacFarland. 



Fig. 94. Detail of head, or hinge region of right mandible, inner 

 surface, a., superior margin; b., inferior margin; c., 

 the fulcrum, bearing double longitudinal crests bound- 

 ing a longitudinal groove, into which the single crest 

 of the left mandible fits ; d, ventral margin of the an- 

 terior portion of the masticatory process, x 45. 



Fig. 95- Detail of head region of left mandible, inner surface. 

 Lettering as in preceding figure. The fulcrum, c., 

 bears a single crest, x 45. 



