S. r. SntlfJi — KitrJj/ Stat/es <}f Tfijypa t<dpoi(la. 315 



tlio rostrum and lateral spines are enormously developed, suggests 

 the possibility that MtlUer had observed only imperfectly developed 

 young zoea^ in which the rostrum and lateral spines were not ex- 

 pamled. It seems scai'cely probable that such a difterence could 

 exist between the first stage of the zoea, when the veiling membrane, 

 in which, on first escaping from the egg, the young are usually 

 enveloped, has been entirely cast oft' and the lateral spines and the 

 rostrum are fully expanded, and tlie second zoea-stage about to be 

 described. The three later, true zoea-stages obtained are evidently 

 contiguous steps in the development and are here designated the 

 second, third, and last stages of the zoea. From this last stage the 

 zoea passes at once into a stage closely resembling the adult in gen- 

 eral form, but with the eyes still very large and the abdomen furnished, 

 with powerful swimming legs. This condition of the animal corres- 

 j)onds perfectly to the Brachyuran megalops and may properly be 

 designated as the megalops-stage. 



Second zoea-stage. 

 In this stage the young (Plate XLV, fig. 1, ventral view) are a 

 little over 8""" in length, from tip of rostrum to the posterior margin 

 of the carapax, and a little over 2"'"' between the tips of the lateral 

 spines. In general form the carapax is oval, with the smaller end for- 

 ward, and its surface is very smooth and regularly rounded. The dorsal 

 surface of the carapax is strongly convex but very regularly rounded 

 and wholly devoid of any rudiment of a dorsal spine, which is so 

 generally characteristic of the zoeae of Brachyura. At the bases of 

 the ocular peduncles the carapax is shai-ply contracted laterally into 

 an exceedingly long^ very slender, and slightly tapering rostrum 

 curved regularly downward until, toward the tip, it becomes nearly 

 parallel M'ith the posterior margin of the carapax. The lateral spines 

 are nearly as long as the diameter of the carapax, are situated far 

 back and low down on the sides of the carapax, and are directed 

 downward and obliquely outward, but are not strongly curved. 

 Beneath, the carapax ciirves inward on all sides, leaving a compara- 

 tively small opening which is wholly inferior, with its anterior j)ortion 

 about as broad as the telson, but posteriorly contracted into a narrow 

 abdominal sinus, of which the rounded posterior margin is nearly on 

 a line between the lateral spines. This shortening of the inferior 

 opening, carrying the abdomen forward and wholly beneath the 

 carapax, together with the absence of the dorsal spine, gives the 

 animal an apj^earance unlike ordinary Brachyuran zoese. 



