644 Brady and Norman — Monograph of the Ifarine and Freshwater Ost?-acoda 



the length ; end view ovate. Length of Pacific 3 8*4 mm. Length of Atlantic 

 ? 7 mm. ; height 5-8 mm. 



Antennules in ? (fig. 2) have the second joint only slightly longer than 

 the third, which on the front side is much longer than the fourth, and equal 

 to the fifth; sixth and seventh very short; second joint with eight anterior, 

 two lateral, and four posterior simple setse ; third joint witli seven anterior 

 and two posterior setas ; fourth with three distal anterior and three distal 

 posterior setae, this joint is considerably longer on the anterior than on the 

 posterior margin ; fifth bearing on the distal posterior extremity a long-ringed 

 seta, beset on all sides with sensory filaments ; sixth with one long and one small 

 ringed seta; last joint with two long, and four short ringed setae of varied form; 

 the three longest setae (one on penultimate and two on last joint) have long cilia 

 here and there as usual in these setae. Antennae having the swimming branch 

 furnished with twelve setae, the last joint being very broad and bearing five of 

 these setae ; a spine at the base of each seta ; the lowest seta is short, but not 

 spinose on the edge ; the appendicular branch (fig. 3) in ? of similar character to 

 that of Cypridina, consisting of a short, basal joint which has about five small 

 setae, a second much longer joint with one distal seta, a third which tapers to a 

 point as a long, slender, ringed seta. 



Mandibular limb (fig. 4), furnished at the base with a cleft, hirsute process, 

 similar to that in the genus Phihmedes, present in both sexes ; at the base of 

 tlie first joint of the palp are two spines which have five or six spinules on 

 the upper part of one side (fig. 4 a) ; there are also six setae on the distal 

 portion of the front margin, whence also springs a bisetose appendage, which 

 extends be^'ond the short following joint, on the hinder margin is also a 

 single, greatly developed, ringed and ciliated seta, which equals in length the 

 whole of the rest of the limb ; second joint of palp very short, fully twice as 

 wide as long, hinder margin with a fascicle of six setae of various lengths, some 

 of which are ringed and ciliated; tldrd joint of equal width throughout, and 

 three times as long as wide, front margin densely clotlied with setae, hinder margin 

 with a group of about six setae at the extremity ; last joint terminating in two, 

 long, equal nails, and two or three small setaj. The four succeeding limbs bear a 

 close general resemblance to the same organs in Ci/pridina. The first (fig. 5) has 

 three lateral lobes wider than usual, and over-lapping each other, each furnished 

 with many terminal setae ; the palp is three- jointed, with one seta at the end of 

 the first, and two at the second joint ; last joint broad at the extremity, ending in 

 several ungues and setae; second maxillae (fig. 6), having the tooth-lobe furnished 

 with very strong falcate teeth (fig. 6 h), graduated in length from the largest and 

 u]-)permost to that which is most deeply seated ; the teeth are denticulated on the 

 inner face ; vibratory lamina with more than ninety marginal setae. 



