38 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



Brevoortia pectinata, (Jenyns) Gill. 



Diagnosis.— Proportions of head and jaws as in B. tyrannies. Height 

 of body almost three-eighths of total length, and greater proportionally 

 than in B. tyrannus. Fins nearly as in B. tyrannus, but uniformly aver- 

 aging slightly more; the height of the dorsal somewhat less than three- 

 twentieths of total length ; that of the anal equal to or slightly less 

 than half the length of the maxillary. The caudal fin is somewhat 

 longer and more furcate, the length of the external rays never being less 

 than five-sixths of the length of the head, while that of the medial rays 

 remains proportionally the same as in the species first described. Inser- 

 tion of ventral somewhat behind tip of pectoral, this fin and the dorsal 

 being uniformly somewhat farther back than in B. tyrannus ; the inser- 

 tion of the latter from one to four one-hundredths posterior to a point 

 equidistant from the snout and the base of the median caudal rays, and, 

 as in B. tyrannus, behind the vertical from the insertion of the ventrals. 



Scales very large, considerably serrated, and arranged regularly in 

 18 to 20 transverse and 50 longitudinal rows. Scales forming sheath at 

 base of pectoral not large. Operculum smooth, or with inconspicuous 

 and few striations. Squamation upon lobes of caudal extensive and 

 coospicuous. 



Variations. — The variations in the individual specimens studied are 

 not of great importance, and are indicated in the table of measure- 

 ments. 



Table of Measurements. 



Current number of specimen 



1709. 

 Paraguay. 



M. C. Z. a. 

 Pio Grande. 



M. C. Z. b. 

 Pio Grande. 



Aver- 

 age 





Millim. 



lOOths. 



Million. 



lOOtbs. 



Millim. 



lOOths. 



100 th*. 



Extreme length 



•230 



224 





209 



Body : 



30 



83 

 21 



18 



54 

 12* 

 



70* 

 7 

 



6i 

 24 r 

 20 



32 

 M 



18 



b] 





36 

 30 



14 



16* 



51 

 12 



G 



72 

 4 



3G 



31 

 •21 

 14 

 17 



52} 

 12 

 



71 



6 



4% 



Head : 







30 

 •21 

 13 

 10 



53 

 12 

 



10 

 

 4 



| 

 25 

 27 



29 

 47 

 17 



48 



8 





Distance from snout to nape 









Length of maxillary 

















Dorsal: 



Distance from snout 









Length of longest ray 

















Anal : 



Distance from snout 









Length of longest ray 















Caudal : 



Length of middle ravs 









• L J 



Length of external rays, superior 









inferior 









28 



30 

 47 

 18 



49 



8* 



ft 



301 



48 



17$ 



49* 



Pectoral : 



Distance from snout 

























Ventral: 



Distance from snout 









Length 











II. 17 

 I. 21 

 abt. 50 



II. 17 

 I. 20 



4!) 

 20 



II. 17 

 I. 20 

 49 













Number of scales in lateral line 













ant. 80 







20 















