PLATE I. 



Figs. 1-4. Transverse sections of the head of Ceraurus pleurcxanthcmus. Slightly 

 enlarged. 



s. Dorsal shell, 



h. Hypostoma. 



c. Cephalic cavity. 



6, b. Branchiae. 



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, k, b, b. As in preceding figures. 



4, 4. Fragments of thoracic legs. 



0, 0. Portions of cephalic legs. 

 V. Visceral cavity, i 



Figs. 6-10. Sections of the head of Calymene, senaria. With the exception of Fig. 

 10, which is enlarged to three diameters, all are enlarged to five di- 

 ameters. 

 s, V, h, b, b. As above. 



1, 2, 3. Anterior cephalic legs. 

 4, 4. Posterior cephalic legs. 



71, Figs. 8 and 9. Natatory joints of the posterior cephalic legs. 



a, a, Figs. 6 and 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. 



