HOMOLOGIES AMONG CRUSTACEA. 105 
nervous system should be especially noted. In looking 
for the heart remove the top of the carapace where you 
see the depression just behind the line between head 
and thorax. 
Summary of Drawings. (a) Side view of shrimp 
X 4 (omitting appendages). 
Fic. 91.—Crayfish Appendages. 4, antennule; 4, antenna; C, man- 
dible; D, second maxilla; Z, second maxillipede. 
(6) The carapace seen from above X 4. 
(c) Side view of thorax with carapace removed to 
show gills x 4. 
(d) An eye seen from above X 6. 
(ce) Large antenna x 6. 
(f) Small antenna X 6. 
(g) First, second, and last leg X 4. 
