374 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.39. 



are developed within the segments in front of it, until finally in the 

 fully mature adult it may almost disappear. 



The maxillipeds are three-jointed appendages, with the basal joint 

 in proper position behind the otlier mouth-parts. It is therefore only 

 in the very last stage of development that they become abortive and 

 the basal joint disappears to a greater or less degree. On the con- 

 trary, the first maxillae are rudimentary from the very beginning and 

 are never developed any more than we see in the adult. 



This species is found occasionally upon the gills of the gar-fish or 

 bill-fish, Tylosaurus marinus, and is never very common. The Museum 

 collection includes a single lot obtained at Beaufort, North Carolina in 

 1905 and numbered 38622, U.S.N.M. There are a goodly number of 

 specimens, and the lot includes both sexes and development stages. 



BOMOLOCHUS NITIDUS, new species. 



Plate 56; text-figure 8; plate 58, fig. 201. 



Female. — Cephalothorax semielliptical, one-half wider than long 

 and squarely truncated posteriorly; bases of the first antennae widely 

 separated, with a broad rectangular rostrum projecting between them. 

 Free thorax segments diminishmg regularly and rapidly in width, 

 their lengths in the proportions expressed by the numbers 25, 35, 18, 9; 

 genital segment not enlarged, as wide as the fifth segment, with 

 strongly convex sides. Abdomen three-jointed, the joints dimin- 

 ishing slightly in width, the terminal one a little the longest and cut 

 off obliquely at the posterior corners. Anal laminae as long as the 

 last abdomen joint and somewhat tapered, each tipped with two 

 large setae, of which the inner one is considerably longer than the 

 outer, and three shorter ones. Egg-cases large and cylindrical, half 

 the entire length and nearly twice the diameter of the genital seg- 

 ment; eggs large, arranged in six or seven longitudinal rows, about 

 seventy-five in each case. 



First antennae stout but rather short, scarcely reaching the lateral 

 margin of the carapace, and very indistinctly segmented, even the 

 terminal portion. These antennae are sparsely armed with short 

 setae, large and flattened at the base, smaller and hair-like toward the 

 tip. Second antennae of the usual pattern for this genus. 



Labrum almost circular, with evenly rounded margins and a smooth 

 surface; mandibles small and weak, the cutting blade short and 

 smooth. 



First maxillae large and swollen, each armed with three widely 

 divergent setae. Second maxillae with a large and stout basal joint, 

 the terminal cutting portion bipartite, each ramus acuminate and 

 covered with short hairs. Maxillipeds of good size and placed well 

 forward, the terminal claw smooth, without teeth or branches, and 

 armed with a smgle medium sized plumose seta at its base. 



