42 MEMOIRS OF THE QUEENSLAND MUSEUM. 



patch well developed but narrow; apical teeth long; subapical elements (one 

 or two rows) broader than long, with a raised phalangiform median structure,, 

 corresponding to the shaft of the apical tooth. These scales are much smaller 

 than those of S. maculata, and also narrower, but the structural characters exactly 

 agree. 



GERRID^E = XYST^EMID^]. 



There is also a family Gerridag in Hemiptera, based on Gerris. As the 

 insect family appears to have priority, the Gerridse of Ichthyology may take the 

 name Xyst^mid^e. 



Xystsema darnleyensis Ogilby. Darnley Island. Scales broader than 

 long, about 5-7 mm. broad and 4§ long; about 3 to 5 widely divergent, rather 

 weak basal radii ; lower margin undulate ; nucleus above the middle ; circuli 

 extremely fine and dense, transverse, confined to the region level with and below 

 the level of the nucleus ; apical field without sculpture ; apical margin simple. 

 In some scales the nucleus is surrounded by 5 or 6 complete (circular) circuli, 

 and the circuli for some distance beyond are also circular, but cut off above at 

 the level of the nucleus. The laterobasal circuli also curve upwards, reaching 

 the margin at a very acute angle, though the uppermost lateral circuli reach it 

 practically at a right angle. 



This is a typical Gerrid (Xystamiid) scale, except that it has lost the 

 last rudiments of the ctenoid patch. In Gerres rhombeus (Mindi Cut, Panama 

 Canal Zone ; Meek and Hildebrand) there is a triangular weakly ctenoid patch, 

 the lower corner elongated and pointing to the nucleus. In Eucinostomus cali- 

 forniensis (Mindi Cut; Meek and Hildebrand) the ctenoid patch is broad, and 

 the circuli are completely transverse, even at the laterobasal corners. Thus 

 E. calif or?iiensis is most specialised as to its circuli, but X. darnleyensis has 

 gone farther in the direction of the loss of ctenoid elements. 



POMACENTRID.E. 



Amphiprion percula L. Darnley Island. Scales subquadrate, about 

 1 mm. broad and | mm. long ; nucleus a little above the middle ; basal radii 5 to 

 7, very distinct; basal margin crenate or scalloped; circuli normal; ctenoid 

 patch very well developed ; marginal teeth sharp, with broad bases. 



These differ from other Pomacentrid scales seen in having the circuli 

 relatively much less dense, and the lateral margins of the apical teeth more or 

 less concave instead of straight. The subapical ctenoid elements are inclined 

 to be more or less bottle-shaped. 



EPHIPPID.E. 



Scatophagus aetate varians de A T is. Queensland. Scales very small, 

 diameter about 1-1£ mm. ; quadrate, as broad as long, or considerably broader 



