n. 



Oli tlie Young Stages of the geiius Zeiigoptenis. 



By C. G. Joh. Petersen. 



(Witli Olie Plate.) 



P r e f a C e. 



Though the genus ZeiKjopterits is of little cousequence iu practical 

 lishery, and oul_y one species, the megriui [Z. megastoma), has auy raarket- 

 vaUie, it is not witliout use to Icuow its fry; if for no other reasoD, iu order 

 uot to mistake it for that of other common fiatfishes, aud thus diaw wrong 

 couchisious as to the occurreuce of the latter. The determin atiou of the 

 frj' of these tishes has already cansed much difficulty. Through the kindness 

 of Professor R. Collett, of Christiania, and Dr. E. W. L. Holt, of Duhhn, 

 who liave sent me material for which I beg to express my best thanks, it has 

 beeu possible for me to remove some of these difliculties, by studying Ihis 

 material in fonnection with what has beeu gathered by the Danish Biological 

 Station and the Thor. I have thought it proper, therefore, to publish these 

 investigations, though I do not yet know the young of the southmost 

 species, Z. miimaculatus, but only of the four other species: the three which 

 are found in Denmark, Z. norvegicus, Z. pimckifns, and Z. megastoma, and 

 the fourth, Z. hoscii which, besides elsewhere, lives also near England. 



In 1893 E. W. L. Holt in "Scient. Trans. Royal Dublin Society", vol. 

 5, ser. 2, table II, gave pictures of a series of sinistral Hatfish, from c. 

 G — c. 10 mm in length, without any spines on the head, and with a peculiar 

 developmeut of tiie caudal fin (two are rejiroduced on my table I, tig. 6 — 7). 

 In the same work, table 12, he gives pictures of 2 other 3'oung flatHsh, 

 evidently also belouging to a sinistral flatfish with a similar pecuhar develop- 

 meut of the caudal fin, but further characterised by a pair of large 

 "otocystic" spines on either side of the head and by a peculiar, striped 

 pigmeutation on the fins and the interspinous bones (see m\' table I, fig. 

 1 — 3). These two types of young ones, the smooth type and the spiny 



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