The Soft-finned Teleostei 357 



The oldest known genera seem to be Clupea and Crosso- 

 gnathiis from freshwater Neocomian strata of the Voirons. 

 Pictet {241) regards the latter genus as intermediate be- 

 tween the Leptolepidae and Teleostei, while most ichthyolo- 

 gists now place it in or near the Clupeidae. Woodward 

 (/(^o: Introd. VII) writes: "The true clupeoid fishes date 

 back to the beginning of the Cretaceous period, and their 

 skeleton is so closely similar to that of the typical Jurassic 

 Leptolepidae, that they may well be direct descendants of 

 the latter." It follows that if the Leptolepidae were all 

 freshwater in origin (p. 344), and largely remained so, 

 the Clupeoids would naturally show freshwater ancestry 

 and affinities. 



By the time of the upper Cretaceous, the family, as the 

 writer would Interpret, tended to split up into one series 

 typified by Pseudoheryx, the types of which became the 

 forerunners of many Acanthopterii, and these early passed 

 largely into the sea. Another series that remained soft- 

 finned split up into groups the species of which retained 

 freshwater existence, like Halecopsis of the London Clay, 

 also some species of Diplomystiis (Fig. 34, p. 238) and 

 Clupea. Others became anadromous, and are now repre- 

 sented by the Thwaite, Allis, and American Shad, which 

 live a considerable part of each year in rivers where they 

 spawn. Still others became permanent sea-dwellers, though 

 "none belong to the deep-sea fauna." The species of 

 Histiothrissa, Scombrochipea, and of Pseudoheryx from 

 the marine chalk of Mt. Lebanon, also the species of Clupea 

 from Monte Bolca and Miocene beds of Italy, are examples 

 of the marine forms. 



In contrast to the Osteoglossidae, the Clupeidae remain- 

 ed almost wholly a northern hemisphere family, though it 

 Is instructive to find that some species and even genera 

 extend down along the coasts of S. America and India to 

 New Zealand. 



Though not as yet known from Cretaceous strata the 

 family Salmonidae may next be studied. For Its close 

 natural affinity to the Clupeidae, Its comparatively primitive 

 teleostean structure, and its present geographical distri- 

 bution, are all of importance. Like preceding teleost 



