236 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.42. 



rated to their very bases and not quite meeting on the midline. Dor- 

 sal plates on the fourth segment ovate, widened posteriori}^ so as just 

 to meet, one-eighth wider than the first pair and projecting behind 

 the latter only one-fifth of their length. 



Genital segment one-fourth wider and longer than the carapace, 

 with strongly convex sides and well-rounded posterior corners; pos- 

 terior sinus wide and deep, with nearly parallel sides. 



Abdomen one-jointed and triangular, much wider than long, with a 

 narrow, slit-hke posterior sinus ; anal laminae broad, strongly flattened, 

 widely separated, and not reaching the posterior margin of the genital 

 segment, each tipped with three minute spines. 



At the base of the abdomen on either side is a small accessory lobe 

 which doubtless represents the rudiments of the sixth segment. 



The egg strings are relatively narrow, and give evidence of being 

 quite long, though no unbroken ones have as yet been obtained; the 

 eggs are exceptionally thin and very numerous. 



Basal joint of the first antennae swollen, considerably wider but 

 shorter than the terminal joint, both joints sparsely armed with setae. 



Second antennae stout, the terminal claw strongly curved ; maxillae 

 in the form of flattened plates on either side of the base of the mouth 

 tube. In the maxillipeds the pad on the basal joint is large and 

 swollen, the terminal claw is long and stout and fits into a depression 

 in the pad near its inner end (see fig. 16). 



All four pairs of legs are small and rudimentary and destitute of 

 plumose setae, but they are distinctly biramose, the rami of the first 

 three pairs two-jointed, with the joints about equal in size, of the 

 fourth pair one-jointed, with minute spines on the exopod only. 



Just outside of each exopod there is a small papilla tipped with a 

 short and weak spine. The fifth legs are in the form of long and nar- 

 row papillae projecting from the ventral surface of the posterior lobes, 

 each tipped with a single short spine. Cement glands similar to those 

 of oblongus, but relatively larger, and with the divisions more plainly 

 visible (see fig. 21). 



Total length, 5.75 mm. Carapace, 2.33 mm. long, 2.4 mm. wide. 

 Both pairs of dorsal plates 1.2 mm. long, first pair each 1.2 mm. wide, 

 second pair each 1.4 mm. wide. Genital segment, 3 mm. long, 3.1 mm. 

 wide. Egg strings, 0.3 mm. wide and at least 8 mm. long. 



Male. — A Nogaus form, short and thickset. Carapace horseshoe- 

 shaped, tlu-ee-sevenths of the entire length, and including the lobes a 

 little longer than wide, with a squarely truncated posterior margin. 

 Frontal plates distinct, separated from the carapace by well-defined 

 grooves, narrowed to a point on the median line, but increasing in 

 width toward the lateral margins, where each ends in a rounded lobe 

 projecting over the base of the antenna; a well-defined but shallow 

 sinus on the median line between the plates. Lateral areas narrow, 



