during their Growth and Development. 113 



scomhus) chrysurus is not one of the forms in which the 

 changes due to age can give rise to the establishment of de- 

 ceptive species. Nevertheless the scapuLar and pra^opercular 

 spines, which are characteristic of so many Scomberoids in 

 the first pliases of their development, are not wanting in the 

 youngest individuals (10-25 millims.) of the series that I 

 have examined. 



The division indicated by G. Cuvier, and effected by Mr. 

 Gill, of the genus Seriola into two distinct genera, Zonichthys^ 

 Swainson, and Halafractus, Gill, seems to be very natural. 

 {S. gigas is the type of a third genus, Naucratopsis, Gill ; and 

 S. Dussumieri and succincta are young forms of Naucrates 

 ductor). To the genus Zonichthys belongs 8. nigrofasciata 

 (with which S. intermedia is no doubt to be united) ; the genus 

 HalatractuSj or Seriola proper, includes 8. Duvierilii, E,isso 

 (with which I identify not only 8. piirpurascens^ Schl., but 

 also 8. 8olandrij C. & V.), 8. quinqueradiata, Schl., 8. zonafa, 

 Mitch, {carolinensis, Holbr.), and 8. rivoliana {8. Boscii^fal- 

 cata^ and honariensis perhaps do not differ from this last 

 species). 8. tajpeinometopon (an example 73 millims. long 

 from the Indian Ocean) is no doubt only a young form of 

 8. Dumerilii^ with the transverse bands which are character- 

 istic of so large a number of young Scomberoids. Young 

 8eriolcB are tolerably frequent in our pelagic collections ; the 

 entire group may therefore no doubt be regarded as subpelagic, 

 and certain forms (such as 8. rivolianci) as completely pelagic. 

 Besides several more or less juvenile forms of *S'. Dumerilii 

 and 8. rivoliana^ our museum possesses very young forms 

 (19-26 millims.) with the head armed with very large spines, 

 and greatly resembling the so-called Xystrophoriis phase of 

 Naucrates ; I have referred them to 8. zonata [carol inensts) ; 

 lastly, young spinous forms of 8. nigrofasciata and 8. quin- 

 queradiata, with regard to which I refer to the figures (pi. iv. 

 figs. 7-11 of the Danish memoir) for the greater or less diffe- 

 rences in physiognomy, the system of coloration &c. which dis- 

 tinguish them from the adults. I think also that we must refer 

 to the subpelagic forms the 8eriolichthys hipinnidatus (the pra3- 

 operculum of which, notwithstanding what has been said, is 

 not denticulated) , as having been observed not only in the 

 Indian Ocean, but also in the Mediterranean and the West 

 Indies. The 8criolellce having been identified with the Nep- 

 tomeni by Dr. Giinther, we must suppose that the armature 

 of spines indicated in them likewise does not constitute a per- 

 manent character. 



