358 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.39. 



TUCCA CORPULENTUS, new species. 

 Plate 49, figs. 116 and 117: Plate 50. 



Female. — Cephalothorax about the same size and shape as in the 

 preceding species, but with the wings divided into four lobes instead 

 of two. Trunk enlarged to three times the diameter of the cephalo- 

 thorax, nearly circular in outline and much flattened dorso-ventrally ; 

 no traces of pits or impressions on either the dorsal or ventral sur- 

 faces. 



Posterior margin evenly rounded, without lobes, and overhanging 

 the genital segment and abdomen so that the latter are invisible in 

 dorsal view. Genital segment and abdomen relatively very small. 

 Egg cases cylindrical, somewhat narrowed at either end, and about 

 the same length as the trunk. Eggs minute and arranged like those 

 in im'pressus. 



First antennae large, four-jointed, and heavily armed with setse; 

 the spine between their bases long and narrow. Second antennas 

 with the two distal joints much stouter than in impressus, the ter- 

 minal one inflated, but with a narrow process and thick, blunt claws. 

 It is thus the exact counterpart of the same appendage in impressus, 

 where the terminal joint was slender, with a thick, blunt process, and 

 narrow, sharp claws. Labrum ovate, one-third longer than wide, 

 with evenly curved margins. Mandibles three-jointed; basal joint 

 no wider than the second joint, the latter carrying on its posterior 

 margin near the distal end a large secondary spine, longer than the 

 terminal joint but not as wide. 



First maxillae similar to those of the previous species, the central 

 seta the largest and longest. Second maxillas with a tripartite tip 

 instead of a bipartite one; the third division is smaller than the other 

 two and is arranged like a palp covering the basal half of the anterior 

 division on its ventral surface. All three divisions are finely toothed 

 along both margins. Maxillipeds much heavier and stouter than in 

 impressus; in particular the terminal claw has a decided S-shaped 

 curve, with a thickly swollen base nearly the size of the basal joint, 

 a short knob or branch on the posterior margin at the distal carve 

 of the S, and a bluntly rounded tip, corrugated by several transverse 

 grooves. 



First and second swimming legs very similar to those of impressus; 

 third and fourth pairs with relatively larger basal joints, each of which 

 has an indentation or notch on the anterior margin opposite the inser- 

 tion of the small endopod. In the third legs there is a spine at the 

 outer distal corner of the basal joint, and three spines on the outer 

 margin of the proximal joint of the exopod. In the fourth legs there 

 is also a spine at the outer distal corner of the basal joint, but none 

 on the proximal joint of the exopod. 



