﻿REVIEW OF GENUS DOROSOMA — MILLER 



403 



Guatemala^ have shown that the gizzard shad does not occur on the 

 Pacific slope in these countries. 



Variation. — Counts of fin rays, scales, and ventral scutes were 

 recorded for 19 to 185 specimens (tables 2-4). Unfortunately, most 

 of the scales were missing from a large number of the new series. In 

 addition, 24 proportional measurements were made on each of 27 

 specimens (table 8). Although more material is needed from Sonora 

 and southern Sinaloa, the anal-ray counts strongly indicate that there 

 is a definite increase in number southward (table 9). There is con- 

 siderable variation in proportional measurements, as in the predorsal 

 and prepelvic lengths, the width of the interorbital, the length of the 

 snout, the length of the dorsal filament, the size of the dorsal, pectoral, 

 and pelvic fins, the length of the anal fin base, and the length of the 

 lower lobe of the caudal fin. That these measurements are affected 

 to some extent by variation in age is clear (see section on "Changes 

 with Growth"), and it is believed that sexual dimorphism may also be 

 a contributing factor. Evidence that the variations are largely 

 individual is indicated by the lack of positive geographic correlation. 



Table 9. — North-south variation in number of anal rays in Dorosoma smithi 



> Arranged from northwest to southeast. Rfo Muerto (a distributary of the Rio Yaqui) is approximately 

 135 miles northward from Rio del Fuerte. That stream and the Rio Yecorato and Rfo de Mocorito are 

 nearly equidistant, approximately 40 miles apart. Rio Piaxtla is more than 150 miles southward from 

 Rio de Mocorito and about 370 mUes southward from Rfo Muerto. This geographic spread is emphasized 

 in the table by separating the live localities into three groups. The data for the Rio Yecorato include 2 

 specimens (U. M. M. Z. No. 143185) from a tributary of the Rfo Sinaloa, about 1 mile downstream in the 

 same drainage system. 



As shown in table 5, the length of the mandible and the upper jaw 

 are somewhat longer in smithi than in anale, and this might seem to 

 indicate an approach toward the large mouth of chavesi. Measure- 

 ments of these structures in a comparable series of cepedianum, how- 



' I recently spent over a month collecting fishes along the Pacific coastal plain of Guatemala, working 

 habitats typical of Dorsovia, with negative results. 



