PLA.TE XII. 



ASTROPECTEN RECTUS, McCoy. 



From the Calcareous Grit. 



Fig. 



1. AsTROPECTEN RECTUS, McCoy, p. 129. Section of the skeleton, natural size. 



2 a. Portion of the dorsal surface of a ray enlarged, showing the marginal plates. 

 h. Portion of the ventral surface of a ray, showing the marginal plates, inter-ambulacral 

 bones, and ambulacral avenue magnified. 



