836 <S'. I. Smith — Early Stag(s of Hippatalpoida. 



A zoea from Zanzibar described briefly by Clans, in his recent 

 work on the development of C-rnstacea,* and by him doubtingly 

 regarded as one of the early stages of some species of Albunea, is 

 certainly the larva of some near ally of Hippa^ though the figures 

 and description are scarcely sufliciently detailed for a close compar- 

 ison with the here described zoea-stages of that genus. The zoea 

 described by Claus is apparently in a stage corresponding to that 

 which I have called the third zoea-stage of Hippa^ l)ut it is already 

 much larger than the zoete of the last stage in that genus. As far as 

 can be judged from Claus' imperfect figures and description, the 

 most important character, distinguishing his zoea from that of Hippa., 

 is the presence of the exognaths of the external maxillipeds, which 

 form a third pair of SAvimming appendages somewhat smaller than the 

 two anterior pairs ; all the otiier distinctions seem to be.of minor import- 

 ance. The exognaths of the external maxillipeds are entirely wanting 

 in the adiilt TlippidiB but are present in the Albunida% and their 

 ])resence in the supposed Alhunea zoea, coupled with their absence 

 in the latest zoea-stages of Hippa, tends strongly to confirm Claus' 

 supposition that his zoea really belongs to the Albunidie, and most 

 likely to the genus Albunea. 



From his examination of this so-called zoea of AUmrtea, together 

 with Fritz Midler's note upon the zoea of Hippa emerita, previously 

 referred to, Claus concludes that the larval stages of the Hippa and 

 Alhunea grou}) of crustaceans agree much more closely with the zoea- 

 stages of the Bi-achyui-a than with the larval stages of the Paguroids 

 or any of the JMacrura. The additional evidence, derived from the 

 nearly complete post-embryonal history of Hippa, here presented, 

 al)undantly confirms this view. There is nothing in the zoea- or 

 megal ops-stages of Hippa to recall particularly any of the known 

 early stages of the Paguroids, while there is much that forcibly 

 recalls the Brachyuran zoea and megalops. The only conspicuous 

 character distinguishing the Hippa and Albunea zoea from the 

 ordinary zoe^ of Brachyura, is the absence of a dorsal spine upon the 

 carapax, and this is apparently a distinction of minor importance. 

 Claus has suggested a resemblance between these Ilippoid zoea; and 

 the Erichthua larval stage ; the motions and color of the living zoeae 

 of Hippa do certainly remind one of the early stages of some of the 

 Stomatopods ; l)ut these distant resemblances do not appear to be 



* Untersruchiingen zur Erforschung der fTenealng-ischen Grimdlag-e des Crustaceen- 

 Systems, Wein, 1876, p. 59, plate ix, figs. 1-10. 



