52 MEMOIRS OF TEE QUEEN SLA NJJ MUSEUM. 



^SOME AUSTRALIAN FISH-SCALES. 



By T. D. a. Cockerell, University of Colorado. 



I AM again indebted to Dr. Hamlyn-Harris for an interesting series of scales, Avhich 

 are described below. It may be worth while to give a brief account of the method of 

 preparing scales for study. We first tried mounting them in baisam, which rendered 

 them too transparent and obscured the markings ; after various trials it was 

 discovered that dry mounts were by far the most satisfactory. The procedure is as 

 follows : — 



(1) Remove the scales from the middle of the side of the fish, trying to avoid 



latinucleate (regenerated) scales. 



(2) Place the scales, while wet, on a glass slide, and cover with a cover- 



glass, or, if the scales are large, with a second slide. 



(3) Put on a clamp to keep the cover-glass dowTi and in place, or, if a second 



shde is used, two or three clamps. 



(4) Put on two square gummed labels, each overlapping one side of the 



cover-glass ; or, if a second slide is used, put the labels over the 

 ends, so as to bind them together. 



(5) The next day the clamps may be removed, and the shde is finished. 



Scales hardly ever slip out, but it is best to keep them in flat trays 

 or flat card-boxes. 



If the scales are not mounted when removed from the fish they are best 

 preserved dry in small paper envelopes. They must then be moistened before mounting. 

 The apical part of the scale is covered with skin, which should usually be rubbed off. 



BELONID^. 



Tylosurus impotens Ogilby. Moreton Bay. Scales variable, quadrate, nearly 

 square or broader, large ones about 4-5 mm. long and broad ; apical field extensive, 

 without circiih, but frequently with irregular cracks ; circuli in the basal and sublateral 

 fields concentric, simple, or variously connected by irregular cross-hnes, forming a 

 network, the meshes of which may be verj^ dense in the region about the nucleus. This 

 whole system of crossed lines is of the nature of cracks or interruptions in the scale- 

 substance, and passes into broad cracks which invade the apical field. So far as 

 superficial appearances go, portions of the scales curiously simulate the scales of the 

 Amphibian Ichthyophis. Tylosurus acus, from the Atlantic, differs greatly from 

 T. impotens in the very broad scales, with the nucleus surrounded by circuli, which 

 extend right across in the apical field, not leaving a large sculj)tureless area. In 

 T. acus there are innumerable very fine radiating and transverse cracks, which have 

 nothing to do with the circuli, and when they cross each other do not appear connected, 

 but form a very minutely square-meshed net, as it were of independent strands. 



