Solenogaster Mollusks- — SCHWAB L 
279 
retractor muscles. Only five pairs of gill re- 
tractors are present; the ventral posterior ones 
are lacking. 
The nervous system shows a very compact 
mass of three pairs of precerebral ganglia and 
a markedly bilobed brain, both attached to 
the dorsal wall of the fore-gut; the buccal nerve 
is shortly freed. The suprarectal ganglion is 
surrounded by the pericardium. The fore-gut is 
narrow, triangular in outline where located 
I 
>6ocy<. 
Fig. 27. Crystallophrisson rubrum. Characteristic 
spicules from body regions b, c, and d. 
Fig. 28. Crystallophrisson rubrum. Sta. 2150. 
between the mouth opening and the brain, 
then semicircular in the brain region, and some- 
what widened and quadrangular in the region 
of the radula. Numerous buccal glands are vis- 
ible behind the sphincter and all three kinds 
of salivary glands are present. The radula is 
typical and lacks denticles. The mid-gut is wide 
and has a cuticular region near its opening to 
the liver. The rectum is slightly winding. 
The pericardium is spacious, the ventricle 
slender and not very muscular, with two atrio- 
ventricular openings. The dorsal vessel begins 
with a bulb. Gills are conspicuously small and 
have only a few gill lamellae. The epithelium 
of the gonoducts is not continued on the wall 
of the cloacal chamber. 
DISTRIBUTION: Two specimens come from 
the San Pedro area, southern California, in 
310-386 fm, one from clay sediments, the other 
from mud with glass sponge. 
