334 Memoir Sears Foundation for Marine Research 



dark spot at shoulder, often missing in specimens less than lOO mm long. Fins all 

 plain, slightly yellowish to green in life. Peritoneum generally pale or silvery, often 

 with dark punctulations, and sometimes quite dusky. 



Size. The Graybacks, like the bluebacks {aestivalis), attain a length of about 

 380 mm (15 in.) and a weight of about 14 ounces; the usual length of market fish, as 

 observed in the Chesapeake Bay area, averaged only about 275 mm (i i in.) in length 

 and about a half pound in weight. 



Although Graybacks generally grow to a length of 275-300 mm (11-12 in.) in 

 salt water along the Atlantic coast, their usual length in Lake Ontario {118: 188) 

 is less than 150 mm (6 in.). The same writer mentioned fish only 100-125 mm 

 (4-5 in.) long with roe as further evidence of stunted growth resulting from the 

 local conditions under which the fish were living. 



Development and Growth. The eggs are 1.25 mm in diameter and very glutinous 

 when first laid, adhering to brush, rope, stones, piling, and other objects {lig: 123). 

 The incubation period extends over six days at a mean water temperature of 60° F. 



Recently hatched larvae are very slender and extremely transparent, and have 

 only a row of pigment spots on the side of the tail (JJJ: 506, pi. i, fig. 8). A two- 

 day-old fish is about 5.0 mm long, and Ryder's figure shows the greatest depth, in- 

 cluding the fin folds, to be about 10 times in TL, with the vent (as usual in clupeoid 

 fishes) situated very far back at about the beginning of the posterior fifth of the body. 

 This agrees very well with a larva of similar age and size described as P. aestivalis 

 (j6: 1 26). 3* The appendages (pyloric caeca), connected to the intestine near the 

 stomach, are very small or wanting in the young but become greatly developed with age 

 {59 •• 90). 



The young reach a length of i 5 mm when a month old {16: 109). On the smallest 

 specimen at hand, 29 mm (22 mm SL), taken on June 18 (1873) at Washington, 

 D. C, the depth is 4.0 times in SL; in other respects it already resembles the adult; 

 the eye is notably longer than the snout and remains so throughout life. When the 

 fish reach a length of about 100 mm, the proportionate depth is more or less the 

 same as in adult fish. 



The gill rakers (see Description) increase in number with age, this increase being 

 especially rapid in the young up to about 100 mm SL. In this species, as in P. aestivalis, 

 the teeth are more prominent in the young than in the adults and disappear from the 

 premaxillary with age. 



The young reach a length of 50-100 mm (2-4 in.) by autumn in streams trib- 

 utary to the Gulf of Maine {16). This rate of growth is about the same as that 

 shown by Hildebrand and Schroeder {59: 91) in a table based on collections made in 

 streams tributary to Chesapeake Bay (especially the Potomac River). This table in- 

 cludes: 26 young for June, 45-74 mm; 105 for August, 50-84 mm; 134 for Sep- 



34. Early larvae and some young adults, supposedly of P. pseudoharengus, were described and figured by Prince 

 (/05: 103-108, pis. 8, 10, in part). It seems doubtful whether his identifications were correct, for his drawings of 

 young adults, compared with young adults from the Potomac, now before me, show the body to be much deeper 

 and the mouth nearly vertical. 



