138 University of California Publications. [Zoology 



Paracytheroma pedrensis no v. sp. 



PI. 18, figs. 3-12. 



Shell of both male and female, in side view, nearly oval in 

 outline, highest toward the posterior end ; nearly twice as long as 

 greatest height ; shell thin, delicate, transparent : the ventral mar- 

 gin curves in somewhat in its anterior half ; the dorsal margin 

 regularly curved, the arch being boldest posteriori}^ ; anterior and 

 posterior margins regularly arched, passing over gradually into 

 the dorsal and ventral margins, posterior arch bolder than ante- 

 rior ; seen from above, bluntly wedge-shaped, widest posteriorly : 

 strongly compressed, greatest width equal to about two-thirds the 

 greatest height. The inner line of the shell originates near the 

 anterior end of the hinge, curves forward and downward forming 

 a broad, blunt arch; the ventral portion of the line runs almost 

 parallel to the external margin of the shell ; posteriorly it forms 

 another regular arch which is not so blunt as the anterior one; 

 dorsally the line ends near the posterior end of the hinge. 



Length of both male and female 0.57 ; greatest height 0.3 mm. 



Several individuals were found in a plankton catch which was 

 made in the vicinity of San Pedro, California, on July 20. 1901. 



Myodocopa Sars, 1865. 



Shell usually with an antennal sinus. Basal joint of antenna 

 large, pyriform, bearing two branches ; primary branch natatory, 

 with one, rarely three elongated joints, beyond which are at least 

 six short joints which bear setae ; secondary branch small, usually 

 larger in male than in female and formed for grasping. Mandi- 

 bular palp and first maxilla without branchial appendage. Furca 

 broad, flattened, bearing at least three strong claws or spines. 



Family CYPRIDTNIDAE Baird, 1850. 



Shell calcareous, strong, usually with a distinct rostrum and 

 antennal sinus. Antennule with five to eight joints; fifth joint 

 always with a sensory organ in the male, frequently in female. 

 Principal branch of antenna usually nine-jointed; secondary 



