50 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxi. 



onal stages, and through almost all larval stages; they seem to be 

 ready to leave the marsupium, for it is clear that they need only to 

 stretch out their appendages in order to be able to use them for free 

 swimming. 



ii. GNATHOPHAUSIA SCAPULARIS, new species. 

 Plate II, fig. 3a-3c. 



Type and cotype. — U. S. National Museum, 2 males, U. S. Bureau 

 of Fisheries steamer Albatross, Station No. 2992, Revillagigedo Islands, 

 Lower California; 460 fathoms. Cat. No. 32327. 



Near G. zoea, but easily recognized by the anterior constriction of 

 the carapace and the greatlj r expanded branchiostegal lobes. 



Shape of body rather stout. Carapace covering almost completely 

 the first abdominal segment. Postero-dorsal spine indistinctly denticu- 

 late toward posterior margin of carapace, rather short, projecting to 

 about the middle of the second abdominal segment. Rostrum short, 

 much shorter than carapace, denticulate. Supraocular spines strong. 

 Antennal spines small, but distinct. Branchiostegal spines wanting. 

 All keels of carapace well developed. Median keel uninterrupted. 

 Upper lateral keels strong, curved, including a lanceolate, almost plane 

 upper face of the carapace, widest anteriorly. Anterior ends of upper 

 lateral keels strongly curved downard. In front of the anterior ends 

 of these keels the carapace is suddenly constricted and depressed, thus 

 forming a very marked shoulder on each side. This constriction 

 affects greatly the course of the lower lateral keels, which suddenly 

 begin to converge at a point just above the branchiostegal lobes. 

 Above this point and below the anterior end of the upper lateral keel 

 there is an almost pit-like depression, which sends a slight groove 

 upward, toward the median keel. For the rest, the lower lateral keel is 

 similar to that of G. zoea, curving up behind toward the postero- 

 dorsal spine. It projects, however, in its whole length, considerably 

 be} T ond the keel of the lower margin of the carapace. Thus the whole 

 carapace becomes rather prismatic, almost hexangular, the upper face 

 being flat, but interrupted by the dorsal keel, and the lower surface 

 being wanting (between the two lower margins); compare the cross 

 section of the carapace, Plate II, fig. 3c. 



Branchiostegal lobes rounded, vault-shaped, and greatly expanded, 

 rendering the carapace at this point as wide as in the middle, in spite 

 of the great constriction above the branchiostegal lobes. 



Abdomen very similar to that of G. 20m, practically identical with it. 

 Five anterior segments slightly keeled dorsally, with a small, posteri- 

 or^ projecting spine at the hind margin. On each side a blunt sub- 

 dorsal keel. Epimera with the anterior lappet small and rounded or 

 slightly angular; the posterior lappet produced into a sharp spine. 



