S. I. Smith — E((rh/ Stagefi of Hippa talpoida. :i21 



fourth the horizontal diameter of the carapax and the ocuhir pedun- 

 cles are slightly shorter, proportionally, than in the earlier stages. 



In the antennulffi (Plate XL VI, fig. 5) the segmentation of the 

 tlagellum is carried nearly or quite to the peduncle, which, however, 

 shows no division into segments and no clear separation from the 

 flagellum. The ilagellum itself is composed of six or seven segments 

 which are a little broader than long and of which the terminal one is 

 furnished with three filiform setae, the penultimate and antepenulti- 

 mate with two or three each which are situated upon the inner side 

 at the distal articulations, while there are two similarly situated, hut 

 small and i-udimentary setoe, upon the fourth segment from the tip. 



The antenna? (Plate XLVI, fig. 4) have increased very much in 

 size, and the flagellum is much longer than the peduncle. The 

 peduncle shows but one distinct articulation, which is near the bases 

 of the dentiform processes and apparently represents the articulation 

 between the second and third segments of the fully developed 

 appendage. The dentiform processes («, &, fig. 4) ar-i much more 

 slender and propoitionally smaller than in the third stage, but are 

 armed with the same number of spines at the tips. The flagellum 

 (c, fig. 4) externally shows no indication of segmentation, but, in all 

 the specimens examined, the articulations of the flagellum of the 

 succeeding megalops-stage is distinctly visible beneath the integu- 

 ment, as shown in the figure. 



The labrum (Plate XLVI, fig. 5, J), as seen from beneath, is a 

 conspicuous, somewhat ti'iangular prominence between the bases of 

 the antennula? and the mandibles, with the margins and the inferior 

 surface regularly rounded and without emarginations at any point. 

 The labium (t?, fig. 5) is deeply bilobed, the regularly rounded lobes 

 projecting each side of the oral opening nearly to the tips of the 

 mandibles and having the edges clothed with microscopic hairs 

 throughout. 



The mandibles (Plate XLVI, fig. 5, c ; and fig. 6) are almost exactly 

 as in the earlier stages. They are wholly without molar areas and 

 terminate in narrow crowns, which are only slightly different on the 

 right and left sides. In each mandible the inferior half of the coronal 

 margin is armed with four stout teeth, tlie two most inferior of which 

 are stout and obtusely pointed, the inferior being straight and much 

 longer than the next, which slightly overlaps it at base, as seen from 

 before or behind, and curves upward at the tip ; while the two suc- 

 ceeding ones are short, triangular, more acute, and separated from 

 each other by a considerable sinus. On the right side the inferior 



