S. I. Smith — Earhf Stages of JJippa talpolda. 827 



approach so closely that the bases are nearly in the same line, those 

 of one series alternating with those of the other. The teeth them- 

 selves are much shorter than the secondary setae of the outer setae, 

 being -05 to -07'""' long, much stouter and less crowded, so that there 

 are about an hundred in the space of a millimeter in the middle 

 portion of the setaj. Near the base of the seta, a few of the teeth are 

 very slender and haii'-like, but the rest ai-e stout, truncated at the 

 tips, lamelliform, and placed with their bases transverse to the shaft of 

 the seta, but with the blades twisted nearly half way round, so that 

 the surface at the tip is nearly at a right angle to the base. The shaft 

 of the seta itself extends a little way beyond the teeth in an acutely 

 cultriform tip. 



The oral appendages (Plate XLVI, figs. 8, 9, 13 ; Plate XL VII, 

 figs. 3, 4, 6, 7) have undergone a transformation even more wonderful 

 than the usual change from the zoea to the megalops. The mandibles 

 have lost, almost entirely, the structure and function usual to them in 

 all the Thoracostraca, and, together with the other oral appendages, 

 have assumed very nearly the adult form. 



The labrum, as seen from beneath (Plate XLYI, fig. 8, «), is much 

 more elongated than in the zoea-stages, being about as broad as long, 

 but with the sides still arcuate outward and not at all incurved as in 

 the adult. The labium (e, fig. 8) is divided very deeply into two long 

 and obtuse lobes, fringed with microscopic hairs along the oral 

 marp:ins, and projecting forward, each side of the mouth, to the 

 coronal portions of the mandibles. 



The mandibles (Plate XLVI, fig. 8, J, c, d) have become thin and 

 foliaceous and completely consolidated with the walls of the oral 

 opening. They have become differentiated, however, into two 

 portions, apparently corresponding to protognath and palpus, or 

 endognath, though these parts are not separated by distinct articula- 

 tions. The protognathal portion (^, fig. 8), corresponding to the 

 entire non-palpigerous mandible of the zoea-stages, is coalesced with 

 the lateral walls of the mouth, except at the broad foliaceous tip, 

 which scarcely i^rojects into the oral opening. The distal margin of 

 this is, however, obscurely dentate, the denticulation varying some- 

 what in different individuals in the same stage (fig. 8, />, and fig. 9), 

 although the mandibles have apparently ceased to perform any of the 

 usual mandibular functions. The endognathal portion (c, f7, fig. 8) 

 evidently represents a palpus with its segments completely coalesced, 

 although the fold between the terminal {(1) and the outer, spinous 

 portion (c) apparently marks the union of the two distal segments. 



Trans. Conn. Acad., Vol. III. 42 April, 1877. 



