Andrews. — Annulus Ventralis. 
EXPLANATION OF PLATES. 
All figures are from camera lucida drawings with Zeiss lenses 2.90 mm. X aa, 
unless others are indicated, and reduced one half in diameter on plates 44, 45, 
46, and to one third in plates 43, 47, and 48. 
PLATE 43. 
Cambarus affinis. 
Fig. 1. Ventral view of removed annulus. 
Fig. 2. Dorsal view of exoskeleton of same annulus. 
Fig. 3. Posterior view of annulus. 
Fig. 4. Anterior view of annulus. 
Fig. 5. Ventral view of annulus of female killed while laying, cleared in clove 
oil; plug and sperm omitted from drawing. 
Fig. 6. Frontal section of exoskeleton of annulus 21 hours after laying. 
Fig. 7. Posterior view of thick transverse section of anterior part of annulus 
to show shape of orifice and of vestibule. 2 X A. 
Fig. 8. Anterior face of a transverse vertical section of the promontory 
showing connection of end of tube and recess, 24 hours after 
laying; the few sperms left in the recess omitted from sketch. 
2 X A. 
Fig. 9. Section more posterior than the recess but in same series as figure 
8 (pi. 43), showing continued median suture and a fracture from 
its inner end. 2 X A. 
Fig. 10. Ventral view of posterior part of left-handed annulus less than 24 
hours after laying, cleared in oil of cloves. Fixed in boiling water, 
the suture has gaped open. The parallel rulings indicate the slits 
leading from the suture to the tube. 2 X A. 
