580 GEOLOGICAL SURVEY OP THE TERRITORIES. 



EXPLANATION OF PLATE XXXIII. 



Fig. 1. Estheria mexicana Clans (Caldwelli, from Kansas). Section through the shell, 

 hinge, and body ; oes, cBsophagus ; oc, larval eye or ocellus ; add, m, adduc- 

 tor muscle of the valves ; md, mandibles; ov, ovary; gl, liver 



Fig. 2. The same, section through the stomach, showing the biliary ducts leading into 

 the stomach from the convoluted liver lobules ; h; brain. 



Pig. 2a. Section through a biliary tube. 



Fig. 3. Eye of E. mexicana ; c, cones ; r, rods. 



Fig. 4. Oblique section through head of E. mexicana; c, cones; ret, retina. 



Fig. 4a. Section of the oesophagus in Fig. 4, enlarged. 



Fig. 5. Section through ganglia {gang) near but posterior to the maxillse, and through 

 the intestine {inf). 



Fig. 6. E. mexicana, ovary ; ep, epithelium. 



Fig. 7. E. mexicana, section through the shell and hypodermis ; sli, shell ; Ic, large 

 secreting cells ; /, fibers. 



Fig. 8. BrancMpus vernalis Verr. Section through the brain and eye, Xi A; 8a, a por- 

 tion from the middle of the brain, xi A. 



Fig. 9. Brancliipus vernalis Verr. Section through the eye ; c, cones ; ref^, retina ; re<», 

 second retinal streak ; r, rods ; g. opt, optic ganglion ; n. op, optic nerve. 

 Drawn by the author from sections made by Mr. N. N. Mason. 



