56 ANNUAL REPORT OF 



Throughout the Devonian and Carboniferous, stout-finned 

 Ganoids appear to have been represented by but this one group of 

 primitive sturgeons. During the Permian, however, a typical 

 "expression point" was reached, when a new suborder arose 

 through various modifications of the skeleton. These latter in- 

 volved atrophy of the upper lobe of the heterocercal tail, special- 

 ization of the fins, and loss of the infraclavicular plates already 

 alluded to. Although represented by but a single genus {Acentro- 

 phorus) in the Upper Permian, the new suborder — known as 

 Protospondyli — blossomed forth in surprising variety and at- 

 tained world-wide distribution during the Trias, giving rise at the 

 same time to a still higher suborder (Isospondyli) . This last con- 

 tinued on during the Jurassic in the midst of the still dominant 

 Protospondyli, until finally in the Cretaceous this and still higher 

 suborders became supreme, practically monopolizing the seas, as 

 do their descendants at this day. 



To recapitulate briefly the history of the sturgeon tribe, we 

 should bear in mind its introduction in the Devonian, its flourish- 

 ing condition throughout the later Palaeozoic, its giving rise in the 

 Permian to a new suborder known as Protospondyli, and its per- 

 sistence with only minor modifications until modern times. As for 

 its Permian offshoot, this group acquired great importance during 

 the Trias, giving forth still higher suborders, and these in turn 

 leading to modern bony fishes. Inasmuch as the fish-bearing rocks 

 of New Jersey are of Triassic age, it is not surprising to find the 

 fauna largely composed of Protospondyli. The occurrence is to 

 be expected here of sturgeon-like fishes, more highly specialized 

 than the primitive Palceoniscidce, and less SO' than the four modern 

 genera of sturgeons and paddle-fishes; and this expectation is 

 realized. 



General Nature of the Boonton Fish Fauna. — Of the half 

 dozen genera represented in the Triassic rocks of New Jersey, 

 and likewise in New England, the one which is numerically the 

 most abundant, and at the same time represented by the largest 

 number of species, is that which has received the name of Semi- 

 onotus. This form, with its abbreviate heterocercal tail, modified 

 fin-structure and absence of infraclavicular plates, together with 

 its ossified arches of the vertebral axis, falls within the definition 



