during their Growth and Developmejit. 109 



culum is very spinous ; the dorsal and anal are low and 

 almost completely retractile within their scalj sheaths ; as in 

 the young Coryphcence and Pterycombi^ the dorsal does not 

 commence so far forward as at a later period, and it is placed 

 further back in proportion as the fish is younger ; the ventrals 

 are composed of a few very fine rays &c. 



9. Nauceates, Nauclerus, and Xystrophorus ; Nomeus, 



PORTHMEUS, LiCHIA, and ChORINEMUS J PaROPSIS. 



Mr. Gill and myself, some years ago, showed that the 

 Naucleri are young forms of Naucrates ; and the synonyms of 

 the celebrated pilotfish {N. ductor) have consequently been 

 augmented by the other probably merely nominal species of 

 Naucrates, by all those of the genus Nauclerus, and by two 

 species referred to the genus Seriola. But it has not hitherto 

 been noticed that Xystrophorus, Rich., is nothing but the 

 youngest form of Naucrates ; moreover, among the first stages 

 of Seriola there are also some which present, in part, the 

 characters of Xystrophorus. The very young Naucrates are 

 among the small fishes which are often met with among the 

 arms, tentacles, &c. of the Physcdice, pretty frequently asso- 

 ciated with Nomeus Gronovii, which is not less pelagic than 

 Naucrates. These little fishes, as well as the young of Seriola, 

 Coryphcena, &c., are also met with in the floating masses of 

 seaweeds. The young of Naucrates and Nomeus constitute 

 the most frequent product of net-fishing in the open sea ; and 

 we thus possess numerous examples of them, which bear 

 witness in favour of their wide geographical distribution. In 

 Nomeus the changes arising from age and development are 

 comparatively insignificant, but, perhaps, only because they 

 occur so early that they have not hitherto attracted attention. 



Porthmeus argenteus, of which our museum possesses an 

 example 74 millims. long, from the coast of Guinea, is not, as 

 has been supposed, a young form of Choynnemus, but oi Lichia 

 amia. As this species must be referred to a different genus 

 from Lichia glaucus, we may very well leave to the latter the 

 name of Lichia, and in future designate L. amia under that 

 of Porthmeus amia (Lac). On the other hand, Lichia calcar, 

 BL, of which I have before me a specimen 25 millims. long, is 

 a young form of some Chorinemus of the Atlantic with four 

 dorsal spines, perhaps Chorinemus saliens. The museum has 

 received a corresponding series of a Chorinemus from the 

 Indian Ocean 25-34 millims. long, with seven spinous dorsal 

 rays, including successive stages up to the perfectly deve- 

 loped although still very young form. For the subdivision 

 of this genus it would be best to employ a difference hitherto 



Ann. & Mag. N. Hist. Ser. 5. Vol vii. 9 



