148 University of California Puhlicatiojis. [Zoology 



cilia. The valves are densely pitted with foveolae which vary 

 someM^hat in size and shape. There are no riblets. 



The frontal organ consists of a short basal portion and a long 

 outer portion which is slender, wdth the exception of an enlarge- 

 ment near the middle. The antennule is five-jointed ; first joint 

 longest, second abont two-thirds as long; third and fourth sub- 

 equal in length, about two-thirds as long as second; fifth very 

 small. The second joint bears one large and two small setae on 

 its upper margin ; third with two setae on the upper, and one on 

 the lower margin at the proximal end, and one on the upper and 

 two much longer ones on the lower margin at the distal end ; the 

 longer of the two latter setae bears plumules in the middle ; at its 

 outer extremity the fourth joint bears two small setae on the 

 upper and a large one on the lower margin ; fifth joint with five 

 large setae about equal in length, and one small seta. 



The basal joint of the antenna is pyriform in outline, some- 

 what longer than broad; swimming branch of the antenna nine- 

 jointed, the first is long and slender ; the second to eighth joints 

 each bearing a seta, the ninth bearing five setae; setae of second 

 to sixth joints naked, the others are plumose, with the exception 

 of the last one on the ninth joint, which is minute and naked. 



The mandible has a bifid masticating process. The mandi- 

 bular palp consists of two joints and a chela ; at its proximal end 

 the first joint bears two serrated masticating spines and two setae 

 on the lower margin ; near its middle this joint also bears two 

 short and a long seta on the lower and two large setae on the 

 upper margin ; second joint large and strong, its outer margin 

 boldly arched and bearing three setae near the middle; outer 

 margin with one seta at the distal end. The distal end of the 

 second joint bears a strong chela ; the outer branch of the chela 

 is shorter than the inner, falcate, smooth-edged, with two long 

 and two short spine-like processes at its inner end ; the basal por- 

 tion of the inner branch is straight, bent abruptly just beyond 

 the middle, forming a hook-shaped apex which closes over the 

 outer branch ; its inner margin is flattened out to a knife-like, ser- 

 rated edge ; this edge bears a small tooth-like process at its proxi- 

 mal end ; at the base of the inner branch, the second joint bears a 

 small button-like nodule which possesses a minute spine. 



