Corkerell—The Scales of Certain Fishes. 77 



Sometimes the angulation of the circuli is to one side of the middle line. 

 Between the circuli are very numerous squarish to suboval plates, cor- 

 responding to the plate-like elements described in the Gadidse, etc., l>ut 

 square or higher than wide, never transversely widened. In the basal 

 region, where the eireuli are longitudinal, the plates fuse together to form 

 longitudinal ridges. In this region the intervals or sutures between the 

 rows of fused plates, the true circuli, are finely and regularly beaded. 



This remarkable scale may perhaps be the key to the understanding of 

 scale structure, and if so, it must he held to confirm the Timsian them \ 

 of the development of scales from placoid-like elements. It is at any rate 

 impossible to doubt that the basal longitudinal ridges between the circuli 

 are formed by the fusion of the small squarish bodies which are seen just 

 above, and gradually pass into the ridges. We also seem to see the 

 manner of origin of the headed circuli of the Osteoglossid;e, etc. On this 

 view, it is easy to understand why the tine longitudinal basal ribrilhe of 

 Albula present a minutely segmented appearance. Such a view will, 

 however, force us to conclude that the Amia calea scale is not primitive 

 in structure, the fine solid longitudinal ribrilhe representing the perfection 

 f the tendency which we observe in Bregmaceros. The relative positions 

 of these fishes in the ichthyological system is certainly against this view, 

 but it is possible that Amia has specialized scales. 



Whatever Bregmaceros may or may not prove in relation to scales in 

 general, it is certainly significant in relation to the two quite distinct 

 groups of Gadoid scales indicated in Proc. Biol. Soc. Wash., xxiv, p. 212. 

 Urophycis and Enchelyopus show headed circuli; in Urophycis regius the 

 basal circuli are practically longitudinal, though converging toward the 

 middle, while followed round to the middle of the apical field, they meet 

 at an acute angle. The Merluccius scale, apicad of the nucleus, shows 

 a line reticulation between the circuli, exactly corresponding with that in 

 \, obythites. 



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