4 <= 
580 GEOLOGICAL SURVEY OF THE TERRITORIES. 
EXPLANATION OF PLATE XXXII. 
Fig. 1. Hstheria mexicana Claus (Caldwelli, from Kansas). Section through the shell, 
hinge, and body; oes, esophagus; 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; 6r, brain. 
FiG. 2a. Section through a biliary tube. 
Fig. 3. Eye of H. mexicana; c, cones; 7, rods. 
Fig. 4. Oukaus section through head of E. mexicana; ¢, cones; ret, retina. 
Fig. 4a. Section of the esophagus i in Fig. 4, enlarged. 
Fig. 5. Section through ganglia (gang) near ‘put posterior to the maxille, and through 
the intestine (int). 
Fic. 6. EH. mexicana, ovary; ep, epithelium. 
Fia. 7, £. mexicana, section through the shell and hypodermis; sh, shell; lc, large 
secreting cells; /, fibers. 
Fia. 8. Branchipus vernalis Verr. Section through the brain and eye, X4A; 8a, a por- 
tion from the middle of the brain, x} me 
Fig. 9. Branchipus vernalis Verr. Section through the eye; ¢, cones; ret!, retina; ret?, 
second retinal streak; 1, rods; g. opt, ‘optic ganglion ; nN. op, optic nerve. 
Drawn by the author from sections made by Mr. N. N. Mason. 
