3IO BULLETIN OF THE BUREAU OF FISHERIES. 



As in the majority of teleosts, radii appear on the scale of Cynoscion regalis only on 

 the anterior side. They begin, usually four to six in number (on the sides of the fish) , at 

 about the seventh circulus, counting from the focus. These usually continue to the 

 periphery. As the scale increases in size, more radii are added on either side of those first 

 appearing, beginning at various distances from the periphery. Proceeding laterally from 

 the long axis, one finds that they extend diminishing distances from the periphery. They 

 are usually symmetrically arranged — i. e., a radius beginning on one side of the axial 

 radius will correspond with a similar radius beginning at the same distance from the 

 periphery on the other side. The points at which radii begin in the main coincide with 

 the annuli. It would, then, be a simple matter to count these points to determine age, 

 but this rule is by no means infallible. Radii often begin between two annuli, and some- 

 times continue for a short distance only and then disappear. But radii beginnings, not- 

 withstanding this variability, are sufficiently constant to afford a valuable means of veri- 

 fying and supplementing the other methods. 



In case we find an old fish on whose scales the annual rings are very obscure, 

 the various aids in combination make it possible to determine accurately the age of 

 the fish or, at least, to count the annuli. When the annuli near the periphery are so 

 near and indistinct as to be indecipherable, the picrocarmine stain will clearly difi'eren- 

 tiate the last two laminae and probably stain the edges of two or three more. The 

 radii origins indicate the intermediate ones. These can be verified by color differentia- 

 tions of polarized light through a selenite plate. We then have the following scheme : 



First annulus: Usually clearly distinguishable. 



Second, third, and fourth annuli: Stain red with picrocarmine; color differentiations 

 by polarized light. 



Fifth and sixth annuli: The last stains red; the next inner stains orange. 



YEAR GROUPS IN LENGTH AND WEIGHT. 



This is a statistical method of verifying the other means of age determinations 

 and must be employed before the age characters of any one species can be settled defi- 

 nitely. Upon measuring a great number of squeteagues the writer found that they fall 

 into groups of different lengths around 20, 26, 31, 37, etc., cm. (Table i and text fig. 2.) 

 These are what Johnston (1904, 1905, 1907, 1909) called "year groups" — those falling 

 around 20 cm. being probably i year old, around 26 cm., 2 years old, etc. If the other 

 means of determination agree with these results, they may be taken as correct. 



Another suggested means of age determination — probably of little importance — 

 is based on the observation of Williamson that the calcareous corpuscles are also built 

 in layers, so that when viewed in section they appear as concentric rings. This, it 

 seems, is due to a difference of calcification, and the rings would probably represent 

 years, but investigations of the structure of these corpuscles have not been sufficient to 

 warrant an opinion as to their value in this connection. At any rate, it would be an 

 extremely difficult method to apply. 



