274 
PACIFIC SCIENCE, Vol. XVII, July 1963 
DIAGNOSIS: Overall length is 20-40 mm; 
greatest width 1.0-2. 5 mm, the largest speci- 
mens coming from greater depths. This variety 
of the well-known C. nitidulum Loven agrees 
with the stem species in its outer appearance. 
Characteristic are the not very swollen pro- 
thorax, the outline of the buccal plate, the short 
but clearly visible dorsoterminal sense organ, 
and its inner organization showing the devel- 
opment and number of muscles of the stem. 
The nervous system is like that of its stem 
species, and the radula similarly has two den- 
ticles. Other similarities include the structure 
of the liver, the epithelium of the gonoducts 
Fig. 19. Crystallophrisson riedli. Characteristic 
spines from body regions a, b, c, and d. 
and anus which continues for a great distance 
on the cloacal wall, and above all by the pres- 
ence of only one atrioventricular opening. 
The variety differs from the stem species 
by its greyish color and by the short but widely 
expanded postabdomen (Figs. 17, 18), which 
contains a large blood sinus surrounding the 
cloacal chamber, reducing the latter to an un- 
usually small cavity. The spines (Fig. 16) cor- 
responding to those of type C (see Fig. 9), 
which are characteristic of the stem form, oc- 
cur only sparsely, whereas spines of types B, 
E, and G (the last only on the postabdomen) 
are abundant. On smaller specimens the spicula 
of type F could be found in great numbers on 
the metathorax, pre- and postabdomen; on 
larger specimens they were replaced by spines 
of type D, showing a distinct keel. Character- 
istic of the variety is the large, clearly outlined 
atrium of the heart which surrounds the supra- 
rectal ganglion. 
DISTRIBUTION: The stem species has been 
widely recorded from both sides of the north 
Atlantic Ocean, the west coast of Sweden, Nor- 
way, Iceland, the North Sea, the eastern coast 
of North America from New Foundland to 
Virginia, and the West Indies; depths have 
ranged from 20-2250 m. The new variety is 
known through 14 specimens coming from 
the San Pedro area of southern California, in 
depths of 12-185 fm, in sediments of mud, 
sandy mud ( 2 specimens ) , and sandy clay ( 1 
specimen ) . 
Crystallophrisson riedli n. sp. 
Figs. 19, 20 
COLLECTIONS: 
2150 (2) in 310 fm, with C. hartmani and C 
rubrum, 
2324 (1) in 400 fm, with Plathymenia bran- 
cbiosa. 
2352 (1) in 420 fm. 
2414 (1) in 177 fm. 
2838 (1) in 394 fm. 
DIAGNOSIS: Individuals range in length from 
15-22 mm and have an average diameter in 
the prothorax of 2 mm. Alcohol preserved 
specimens are gray with a whitish prothorax. 
In fixed state the posterior half of the prothorax 
