inhabiting the JSTeio England Coast. 249 



or both of the species wliich Mr. Faxon and I have observed to (lifter 

 so widely in regard to the megalops-stage. 



The young in the first zoea-stage fignred by Mr. Faxon (pi. 4, figs. 

 1-4) were obtained directly from the eggs of P. chmtopterana and 

 are of course unquestionably of that species. That the later stages 

 figured by Mr. Faxon (pi. 4, figs. 5-15, and pi. 5) do not belong to 

 the same species as the young in the first zoea-stage, is shown by the 

 diflFerence in the length of the dorsal and rostral spines in the first 

 and last zoea-stages, and by the presence, in the zoeae in the first 

 stage, of the central lobe of the posterior margin of the telson, while 

 it is wholly wanting in the zoeae in the last stage. In the several 

 species of Brachyura in which I have examined a series of zoese in 

 different stages, the dorsal and rostral spines are proportionally not 

 much if at all longer in the first than in the last stage, and there is 

 often a considerable decrease in the length of these spines in passing 

 from next to the last to the last stage : Pinnixa is probably not an 

 exception to this rule. Moreover, among the zoeae of Pinnixa taken 

 in Vineyard Sound in 1875, there are a few specimens of the long- 

 spined form which are evidently in the penultimate zoea-stage, and 

 they agree fully with the numerous specimens in the last stage in the 

 length of the spines and in the form of the telson. 



On the other hand the short-spined zoeae which I observed to pass 

 into a megalops-stage agree with the first stage of the zoeae from the 

 eggs of P. cJimtopterana, not only in the length of the spines but 

 also perfectly in the form of the telson, the median lobe of the pos- 

 terior margin being developed precisely as in the zoetB of the first 

 stage and as figured by Mr. Faxon (pi. 4, fig. 2, b). This is sufficient 

 evidence, I think, to show that the short-spined zoeae upon which my 

 observations were based are the young of P. chmtopterana, and that 

 the long-spined form, which both Mr. Faxon and I observed to pass 

 directly from the zoea to the adult form, must belong to some other 

 species. The fact that these long-spined zoeae were very common 

 both at Newport and in Vineyard Soiind would seem to indicate a 

 probability that they belong to some species regularly inhabiting the 

 coast of Southern New England, and consequently that they are 

 likely to prove the young of P. Sayana, — l)ut this is only a proba- 

 bility. That both forms of the early stages belong to species of the 

 same genus (as the genera of the group to which they belong are 

 now understood) there can be no reasonable doubt, since one of the 

 forms has now been traced from the eggs of a well-known species to 

 the megalops-stage, and the other from tlie later zoea-stages to the 

 early, but geuerically characteristic, stages of the adult form. 



