SOME IRISH GASTEROSTEI. Ill 



wanting ventral fins, which, however, are but indifferently deve- 

 loped in the latter genus. For the same cause, amongst the 

 Siluridse, AilicMhys is separated from Ailia. In the Cyprinodon- 

 tidae Tellia is a Gyprinodon deficient in ventrals. In the Cypri- 

 nidse, subfamily Cobitidina, Apua is closely allied to Acanthoph- 

 thalmus, but has no ventrals ; whilst one of the chief difierences 

 between the Clupeoid Opisthopterus and Pellona is that the former 

 is without ventrals, whilst the latter has only small ones*. 



Amongst a number of Sticklebacks (Gasterosteidse) obtained 

 in Ireland were two very distinct species. The one was bright 

 pink on the chest and along the under surface of the body ; whilst 

 the second or more elongated form was of a dull cobalt-blue on 

 the head and chest f- The pink ones had three or four serrated 

 dorsal spines ; the blue ones from two to nine smooth spines, and 

 were either without or with small ventral fins. 



Had I merely captured specimens of this little species (desti- 

 tute of ventral fins), 1 might have been induced to believe that I 

 had discovered a novel subgenus of Qasterosteus. But as speci- 

 mens came to light demonstrating that the ventral spine might be 

 present, and this not due to age or sex, the fact became obvious 

 that the presence or absence of this fin in Qasterosteus is insuffi- 

 cient even to characterize a species. And when one considers 

 that tbe comparative length of the ventral spine to the pubic plate 

 is still looked upon by some ichthyologists as a good diagnostic 

 signification of a species, one is tempted to question the correct- 

 ness of such a' proposition. 



Before entering upon the description of the fishes obtained, it 



* Eespecting the marine fifteen-spined Stickleback, Couch remarks of the 

 development as follows: — "At the precise time of quitting the egg the young 

 were placed under a magnifier of moderate power, when it was observed that 

 .... the belly was protuberant, and in some the ovum was still visibly attached 

 to the body, and, as the point of union was diaphanous, globules could be seen 

 that had passed from the egg to the intestine. No ventral fins could be per- 

 ceived, which is less a matter of surprise that it has been observed in other in- 

 stances ; these organs are the last that go through the process of development " 

 (Fish. British Islands, vol. i. p. 183). 



t Newman observes, ' The Fishes of Scandinavia,' that the G. pungitius, or 

 " sraa sprigg" of Sweden, during the breeding-season, is coloured red about 

 the lower jaw, cheeks, gill-cover, and base of the pectoral. Those I obtained 

 in Ireland wei-e breeding, and of a colour as described above. 



11* 



