Prentiss. — Otocyst CruBtacea. 



PLATE 1. 



All Figures are of Palcemonetes. In Figure 1 anterior is up on the plate ; 

 in Figures 2, 3, and 4 the dorsal side is up, and tlie anterior end in Figure 4 is at 

 the left. Lines numbered 2, 3, 4, 5 in Figure 1 indicate the planes of the sections 

 shown in Figures 2, 3, 4, and 5 respectively. 



Fig. 1. Dorsal view of the basal segment of both antennules, showing otocysts 

 and the arrangement of the hairs in the sac. X 30. 



Fig. 2. Somewliat oblique transverse section, extending from dorsal anterior to 

 ventral posterior, of both antennules and the rostrum, through the 

 posterior ends of the otocysts (compare line 2, Fig. 1). X 64. 



Fig. 3. Transverse section of right antennule through the orifice of the sac, show- 

 ing tectum and otoliths (compare line 3, Fig. 1). X 64. 



Fig. 4. Parasagittal section througii riglit antennule and brain, showing the 

 course of the otic nerve, with a single nerve element drawn diagram- 

 matically (see line 4, Fig. 1). X 64. 



