HERRINGS. 
953 
Genus CLUPEA. 
Mouth of moderate size ( in comparison ivith that of the Anchovies small), the length of the maxillaries being less than 
half (in Scandinavian forms 40 — 48 %) of that of the head. Tip of the lower jaw projecting to a greater or less 
extent beyond that of the snout. Dentition of the mouth feeble, more or less rudimentary. Anal fin not much 
longer ( less than twice as long) or even shorter than the dorsal; its rays less than 30. 
The greater number of the Clupeoids belong to the 
genus of the true Herrings; and the number of species" 
contained therein is great enough to have occasioned 
several attempts to divide it into subgenera. Valen- 
ciennes even distributed its members among several 
genera 6 , which he based principally on the differences 
in the dentition. But Nilsson arrived long ago “at the 
conclusion c that the teeth are highly variable in dif- 
ferent specimens, even of the same species, the bones 
which are furnished with teeth in one specimen being 
toothless in another”. But the Shads — whose dentition 
is as a rule the feeblest — differ so greatly in other re- 
spects as well from the remaining Herrings that they 
may with reason be placed in a separate subgenus 
bearing the name of Alosa. 
Subgenus CLUPEA. 
Body without spots. Lower anterior portion of the outer surface of the operculum smooth (without grooves). 
Dorsal fin set so far bach that the distance between it and the tip of the snout is more than 4 times the post- 
orbital length of the head. No large scales of singular form on the caudal fin. 
Of this subgenus the Scandinavian fauna possesses 
only two species, the Herring and the Sprat, both of 
great economical importance, and so like each other 
that only a practised eye can distinguish between them, 
where they occur, as they often do, in company. In 
modern times the most painstaking student of their va- 
rieties has been the eminent German naturalist, Pro- 
fessor F. Heincke, who has come to the conclusion 
that the difference between them is only gradual, in the 
a About 90 species have been described. 
h Cuv., Val., Hist. Nat. Poiss., vol. XX, pp. 14, cett. 
c SJcancl. Fna , Fisk., p. 489. 
d Die Varietaten des Herings , II, p. 56 (VII Ber. Comm. 
sense that the Herring exhibits races differing from one 
another in the same manner as, but to a less degree 
than, the two species. We have above seen the same 
relation obtain between the Salmons and Charrs, and 
in the present instance too we find that the smaller 
species attains its place in the form-series of the genus 
more rapidly (at a smaller relative size) and more fully 
(with more prominent characters). The larger of the 
two species is the well-known fish, 
rs. deutsch. M.). 
