326 Memoir Sears Foundation for Marine Research 



those present on lower jaw persistent anteriorly, though not with free points in adults ; 

 a permanent narrow band of granular teeth on median line of tongue. 



Dorsal fin with a definitely concave margin, its origin scarcely an eye's diameter 

 in advance of the pelvic fin and usually a little nearer to margin of upper jaw than to 

 vertical from last ray of anal; a narrow sheath of scales at base, incomplete, leaving 

 base of last 4 or 5 rays exposed. Caudal deeply forked, the lower lobe the longer, a 

 little longer than head. Anal low, with straight margin, its origin about equidistant 

 between base of pelvic and base of caudal ; a narrow sheath of scales at base. Pelvic 

 fin inserted near ventral edge and about equidistant between base of pectoral and 

 origin of anal, 1.8—2.6 in head. Pectoral somewhat higher on side, reaching about 

 0.66 of the distance to base of pelvic, 1.2— 1.7 in head. 



Color. Fresh fish bluish above and sides silvery. Rows of scales on back and upper 

 part of side with more or less distinct dark lines in adults. Shoulder with a dark spot in 

 the larger examples, generally missing in individuals less than 100 mm long. Fins plain, 

 generally greenish or yellowish in life. Peritoneum usually, though not always, dark. 



Size. Bluebacks are known to attain a length of about 380 mm (15 in.) and a 

 weight of approximately 13 ounces. However, the usual size of these fish in commercial 

 catches as observed in the Chesapeake Bay area is under 300 mm (12 in.) and a half 

 pound or less in weight. 



Development and Growth. The eggs and early young were described by Kuntz 

 and Radcliffe from material taken at Woods Hole, Massachusetts {j6: 123-126). 

 The eggs are demersal, somewhat adhesive, semitransparent and yellowish, round, and 

 approximately a millimeter in diameter. The development is rapid; hatching occurs 

 at ordinary laboratory temperature about 50 hours after fertilization. 



The newly hatched larvae (Fig. 8 i a) are close to 3.5 mm long and quite slender. 

 In about four days the yolk is all absorbed and the larvae have grown to a length of 

 about 5 mm. The vent in these larvae, as in other clupeids, is situated far back, about 

 at the beginning of the posterior fifth of the body. 



The smallest specimen at hand, 20.5 mm long (16.5mm SL), taken June 17 (1873) 

 at Washington, D. C, is still very slender (Fig. 8 i b), its depth about 7.5 times in 

 SL. Its eye is rather longer than the snout, the maxillary extends nearly to the pupil, 

 and the fins are all developed, the pelvic being inserted about under the origin of the 

 dorsal. In a 25-mm specimen (20 mm SL), the depth is contained 5.0 times in the length, 

 and the pelvic fin is well behind the origin of the dorsal (Fig. 8 i c), as in adults. 

 The 30-mm fish illustrated by Kuntz and Radcliffe (j6: fig. 100) is much deeper than 

 specimens of somewhat similar size now at hand, its depth being about '^.G times in 

 SL; in specimens from the Rappahannock River, Virginia, 34, 35, and 38 mm (28, 

 29, and 30 mm SL), the depth is respectively 4.6, 4.65, and 4.3 times in SL, and 

 specimens even up to 45 and 50 mm long are more slender than the 30-mm one illus- 

 trated. If the proportions are correctly shown, it seems highly probable that the 

 illustrated specimen is not this species. 



When the young fish reach a length of about 80-90 mm they are usually pro- 



