258 Memoir Sears Foundation for Marine Research 



catch them in large quantities; and the supply of some, such as those of the genus 

 Clupea, seems to be almost inexhaustible. Fresh herring are used extensively as food 

 by man in nearly all parts of the world, and in many areas large quantities are eaten 

 after they have been salted and smoked or canned. Great quantities, especially of 

 Brevoortia, are reduced to oil, fish meal (feed for livestock and poultry), and fertilizer. 

 The smaller species and the young of the larger ones serve still another useful purpose 

 in providing extensive forage for larger predatory fishes, many of which enter into 

 the diet of man. Aquatic mammals, birds, and turtles also feed on them. All this 

 food is provided for man and beast at virtually no cost, as the herring feed almost 

 entirely on small organisms that are not suitable food for man or for the other preda- 

 tors named. 



Although the members of the family Clupeidae have no lateral line, nearly all 

 of the species described in this work have numerous mucous pores and canals about 

 the head and shoulders that may in part compensate for the absence of a lateral line. 

 An air bladder with a very thin wall is present in all the species of the genera examined, 

 namely Clupea, Alosa, Pomolobus, Brevoortia, Opisthonema, Harengula, Sardinella, and 

 Etrumeus, and it may be assumed that the other members of the family also have an 

 air bladder. Its walls are so thin and delicate that dissections must be made with care 

 to find it undamaged. 



Range. Herring (Clupeidae) occur in all seas of the world except those of the Arc- 

 tic and Antarctic regions. Many species ascend freshwater streams to spawn, and 

 others live in fresh water permanently. 



Preparation of Descriptions and Location of Study Material. Nearly all Descriptions 

 were prepared directly from specimens, but a few are included for which no speci- 

 mens were available. In such instances it is stated in the accounts that they were 

 compiled or quoted from publications. The specimens used are in the USNM unless 

 otherwise stated. Freshwater species occurring in the rivers draining into the western 

 North Atlantic are not numerous and have been included for the sake of complete- 

 ness ; it is possible that all of these forms occasionally enter brackish or salt water. 



Measurements and Counts. The proportions used in Description are based on measure- 

 ments made with vernier calipers having sharp straight points. Many of the measure- 

 ments of small fish (sometimes even of larger ones) and of the small structures such 

 as eye, snout, and maxillary were made under magnification. See also Measurements 

 and Counts under Brevoortia, p. 343. 



Total length : distance between margin of snout or tip of lower jaw (whichever 

 is longer), more or less along the body axis to a vertical at tip of longest lobe of 

 caudal fin. 



Standard length: distance between anterior margin of snout and base of caudal. 



Body depth: greatest depth unless otherwise stated; this may occur over base of 

 pectoral or as far back as origin of dorsal fin. 



Head: if used without a modifier, the distance between anterior margin of snout 

 and most distal point of bony (not membranous) margin of opercle. 



