22 University of California Publications. [Zoology 



along' rostrum, anterior margin, and anterior two-thirds of ven- 

 tral margin ; a small oval spot along dorsal margin near the 

 postero-dorsal angle ; a quadrangular patch over the large muscle 

 of the antenna ; a narrow band extending from hinder edge of 

 rostral sinus posteriorly and dorsally to anterior edge of hinge. 

 In the female only the anterior margins of the valves are some- 

 times tinged with orange. 



Male. — The capitulum of the frontal organ is dilated and 

 somewhat truncated at the base, with a blunt apex ; hispid with 

 a few short hairs. The antennule bears three long- setae, the first 

 of them is a little longer than the other two and bears in its 

 middle third about forty pairs of very small recurved spines ; 

 the third seta bears a veiy small lamina just beyond its middle; 

 there are two sensory setae, one of which is short, the other is 

 much longer, is dilated near the base, and turned back in oppo- 

 sition to the antennule. The hooked appendage of the secondary 

 branch of the right antenna is bent at an acute angle near the 

 base ; the outer end is distinctly erenulated on the inner margin ; 

 the left appendage is somewhat smaller and not so distinctly 

 erenulated at the end. 



In both sexes the secondary branch of the antenna bears a 

 sensory seta on the last joint with an enlarged basal portion 

 where the walls are rather thick and strong, while the outer por- 

 tion is thin-walled and weak, and ends in a sharp point. 



In the female the frontal organ is straight ; sometimes the 

 capitulum is more or less distinctly separated from the peduncle 

 by a constriction ; hispid with sparsely set minute hairs. 



Length: male 2.4; female 3.1 nun.; height of female 1.2 mm. 



Distribution. AVest coast of South America between Caldra 

 and Antofagasta, 25° S. lat., 72° W. long. (G. W. MiiUer) ; off 

 San Diego, California. 



The name given to this species by Miiller (0. oblonga) was 

 previously applied to another species of Conchoecia {Paracon- 

 choecia oblonga) by Glaus, so the name pacifica is proposed in its 

 stead. 



