Fig. 1. 
Fig. 2. 
Fig. 5. 
Fig. 6, 
Fig. 3. 
Fig. 4. 
Fig. 7. 
Fig. 9. 
Fig.10. 
Fig. 8. 
Fig. 8 a. Enlargement of the ova. 
PLATE IV. 
Head of Ceraurus pleurexanthemus and two segments of the thorax. En- 
larged to two diameters. 
c, Cephalic cavity. 
i, Intestinal canal. 
Transverse section of the thorax of the same specimen. 
Under or ventral surface of the dorsal shell of Cerawrus pleurexanthemus. 
This figure is restored from several specimens; many specimens aro 
entire, but some portion may be concealed by the imbedding matrix 
filling the various depressions in the ventral surface of the shell. 
Longitudinal section of the same, with the outline of the intestinal canal 
and ventral membrane restored. 
s. Dorsal shell. 
h. Hypostoma. 
c. Cephalic cavity. 
v. Mm. Ventral membrane. 
i, Intestinal canal. 
A branchia from Calymene senaria. 
a. Support of the spiral attached to a portion of the basal joint 
of the leg. 
b. Spiral branchiæ, 
Same, from Ceraurus pleurexanthemus. 
Enrolled Calymene senaria, showing a cast of the interior of the ventral side. 
Branchiæ of Cyamus Scammoni Dall, attached to the thoracic segments. 
Branchiæ of Cyamus diffusus Dall, attached to the thoracic segments. 
Longitudinal section of the anterior portion of a Ceraurus pleurexanthemus, 
with ova enclosed within the visceral cavity, 
