PLATE I. 
Figs. 1-4. Transverse sections of the head of Ceraurus pleurexanthemus. Slightly 
enlarged. 
s. Dorsal shell. 
h. Hypostoma. 
c. Cephalic cavity. 
b, b. Branchiæ. 
4, 4. Cephalic legs. 
Fig. 5. Transverse section of the head of the same species, with portions of the 
thoracic appendages. Enlarged to three diameters. 
s, h, b, b. As in preceding figures. 
4, 4. Fragments of thoracic legs. 
o, 0. Portions of cephalic legs. 
v. Visceral cavity. i 
Figs. 6-10. Sections of the head of Calymone senaria, With the exception of Fig. 
10, which is enlarged to three diameters, all aro enlarged to five di- 
ameters. 
8, v, h, b, b. As above. 
1, 2, 3. Anterior cephalic legs. 
4, 4. Posterior cephalic legs. 
n, Figs. 8 and 9. Natatory joints of the posterior cephalic legs. 
a, a, Figs. 6and 8. Portions of the contents of the'space enclosed 
between the dorsal shell and the membrane uniting the 
central visceral cavity and the outer margin of the dorsal 
shell. 
