136 Proceedings of the Royal Irish Academy. 



holds good, as in salmon and trout the banded dark and light zones were not 

 visible in any which I examined. 'J'his fish cannot be called a true deep- 

 water species, and the occurrence of year-rings, as these apparently are, is not 

 surprising. 



Halopoijjhyrus eques, -430-707 fathoms, has comparatively large, oblong 

 scales, closely covered with fine striae wliich converge slightly towards the 

 anterior end of the scale. With oblique transmitted light faint rings are 

 visible, due in part to a slight bending of the striae where they cross the 

 ring. From two to four rings could be made out on different scales of a 

 specimen of 29 cms. In tlie outer part of the scale the spaces between the 

 rings correspond to twoliglit bands, with sometimes an additional incomplete 

 band showing at the anterior end of the scale. 



In Phycis Mennioides, lGO-627 fathoms, the light bands are conspicuous 

 by polarised light, but no ringed markings could be made out. Examination 

 of a small number of scales from Rhombus Boscii, Solea profundicola, and 

 Scorioaena dactylo2:itera revealed no signs of periodic or interrupted growth. 



Through the kindness of Dr. Scharfi' I had an opportunity of examining, 

 in this connexion, the scales of three species of fish from Jamaican waters in 

 the collections of the Dublin Museum, labelled Chaetodon striatiis. Platy- 

 glvssus intcrnasalis, and Mesoprion chrysurus, the last two names being 

 synonyms, according to Jordan and Evermann, of Irido cyanoccphalus and 

 Oxyurus chrysurus. 



In Mesoprion, on four out of seven scales there was an indication of 

 a single growth-ring running round part of the scale, parallel to the 

 margin. It was accompanied by a slight unconformity in the arrangement 

 of the striae, which are parallel to the scale margin, where they run out on 

 to the exposed portion of the scale, and also seemed to be a starting-place 

 for some of the radial grooves with which the anterior part of the scale is well 

 provided. The striae in this species are parallel to the covered margin of the 

 scale and are finely denticulated on their inner side. 



In Chaetodon striatus, which has scales of an almost exactly similar type, 

 no sign of growth-rings was observed. 



Plati/ylo^sud internasalis, with very large scales, lias two systems of ladial 

 grooves, one, as in Chaetodon and Mesoprion, running forwards to the anterior 

 margin, the other backwards to the exposed portion. The striae on the 

 imexposed portion are of the concentric type and finely denticulated. There 

 was no sign of growth rings on the scales. 



From these few examples nothing more can be inferred than that the 

 occurrence of growth-rings is not universal amongst tropical fishes. It cannot 

 be said definitely that the markings on Mesoprion scales are true growth rings. 



