Fig. 36.— Thoracic ribs of Antrodemus valens Leidy. No. 

 8367 tj.s.n.m. \ nat. size. viewed from the front, 

 all of the right side. a, first (?) thoracic rib. b, 

 fourth thoracic rib; c, seventh thoracic rib; d, ninth 

 thoracic rib. i. p. lateral process. 



