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PROCEEDINGS OF THE NATIONAL MUSEUM 



structure definitely has decreased in relative size. Comparing young 

 and adults of I), smithi from single local ties, we see that the dorsal fila- 

 ment increases proportionately with age at least up to a length of 

 122 mm. (table 11). Since no larger specimens were available, I do 

 not know whether the structure shows the growth pattern with increas- 

 ing size that is indicated for anale. The limited data given for D. 

 cevedianum by Hubbs and Miller (1941, p. 235) also demonstrate 

 that there is a general increase with age in the relative length of the 

 dorsal filament from a value (in thousandths of the standard length) 

 of 168 for a specimen 47 mm. long to values of 239 to 285 in size 

 ranges of 115 to 149 mm. long. The single large specimen 245 mm. 

 long gave a value of 258, indicating again that after a certain size 

 range is reached the relative length of this structure appears to 

 remain nearly constant. "When we examine the growth of this 

 structure in D. chavesi, however, we find a complete reversal from the 

 pattern for the other three species. In table 7, it is seen that as the 

 fish increases in size from 84 to 142 mm. in standard length the 

 proportionate length of the dorsal filament decreases from a maximum 

 value of 192 to a minimum value of 129, or from an average value of 

 170 to that of 147. Measurements of three additional specimens 

 (U.S.N.M.J- No. 22138, labeled "Nicaragua") 145, 149, and 188 

 mm. long gave the following values, respectively: 120, 126, and 139 — 

 values averaging far below that for the largest size group given in 

 table 7. Although these data are not as complete as desirable, they 

 indicate clearly that the dorsal filament does not increase in length 

 with age in chavesi as it does in the other species of Dorosoma. 



Table 10. — Proportional meas7irements of Dorosoma anale, at various sizes, showing 



changes with age 



[Expressed in thousandths of the standard length. Compiled in part from table 6] 



Measurement 



Young 



U. M. 



M. Z. 



No. 



143377 



C.N. 

 H. M. 



No. 



4681 



C.N. 

 H. M. 



No. 



3787 



C.N. 

 H.M. 



No. 

 4681 



C.N. 



H. M. 

 No. 

 14628 



28 adults 



Range 



Range 



U.S. 



N. M. 



No. 



61252 



Standard length, in mm 



Pelvic insertion to tip of snout 



Anal origta to caudal base 



Head: 



Length 



Depth 



Eye, length 



Snout+eye 



Dorsal filament, length 



Mandible, length 



Upper jaw, length 



28.0 

 525 

 318 



357 

 289 

 103 

 168 

 89 

 143 

 100 



52.2 

 513 

 368 



339 

 278 

 103 

 165 



125 

 94 



66.7 

 447 

 421 



289 

 232 



85 

 139 

 214+ 



99 



79 



80.0 

 447 

 465 



281 

 229 



79 

 132 

 206± 

 114 



79 



82.9 

 453 

 420 



287 

 252 

 82 

 135 

 233± 



92-149 

 409-454 

 399-445 



253-294 

 200-245 

 61- 76 

 113-130 

 252-319 

 82- 99 

 61- 76 



154-190 

 402-423 

 415H157 



231-261 



189-222 



56- 69 



100-114 



278-314 

 74-84 

 61- 69 



256± 



408 



410 



228 

 205 



56 



99 

 201? 



73 



59 



