PLATE XIX. 



Pygasters from the Inferior Oolite. 



Fig. 



1 a. Pygaster semisulcatus, Phillips, p. 275. Upper surface, natural size. 



b. Under surface, natural size. 



c. Lateral view of the same test. 



d. Ambulacral area, poriferous zones, and two inter-ambulacral plates, magnified three 



diameters. 



e. Primary tubercle, with the areolar circle of granules, magnified eight times. 

 /. Primary tubercle of the ambulacral area, magnified eight times. 



g. Primary tubercle from the base, magnified eight times. 



h. Primary tubercle from the ambulacral area, magnified eight times. 



2 a. Pygaster conoideus, Wright, p. 278. Upper surface, natural size. 



b. Under surface, natural size. 



c. Lateral view, natm'al size. 



d. Ambulacral area, poriferous zones, and two inter-ambulacral plates, magnified two 



diameters. 



e. Primary tubercles from the upper surface, magnified eight times. 

 /. Primary tubercles from the base, magnified eight times. 



