162 Ceraurus pleiirexanthemus. 



EXPLANATION OF PLATE XL 



Figure A. Section of thorax at fourth segment; enlarged to two diame- 

 ters. 

 a. Axial groove. 

 bb. Axial processes. 



cc. Thoracic pleurae and triangular depressions. 

 dd. Circular cavities. 

 ee. Free pleurae. 

 gg. Inner extremities of thoracic pleura?. 



Figure B. Interior of the dorsal shell; enlarged to two diameters. 



1. Hypostomatic suture. 



2. Hypostoma. 



3. "Doublure." 



4. Occipital depression. 



5. Occipital cavity. 



C, 7. Facial sutures cutting "doublure." 



8. Glabellar depressions and processes. 



9. Neck depression. 

 10. Spines of the head. 



a. Axial groove. 



bb. Axial processes. 



cc. Triangular depressions. 



dd. Circular cavities. 



ee. Free pleurae. 



/ Crescent shaped surface on free pleura?. 



m. Elevated margin of the hypostoma. 



rr. Axial processes. 



s. Smooth crescent-shaped surface on " doublure." 



t. Pygidium. 



x. Oval openings. 



z. "Doublure." 



Figure C. Longitudinal section at median line ; enlarged to two diame- 

 ters. 



1. Hypostomatic suture. 



2. Hypostoma. 



3. "Doublure." 



4. Head. 



5. Thorax. 

 G. Pygidiurn. 



Figure D. Section of segment at median line; enlarged to five diameters. 



1. Posterior reflected articular margin. 



2. Outer surface of segment. 



3. Union of articular fold and axial ring. 



4. Articular fold. 



