The Dipneusti and Crossopterygii 309 



Permian of Durham in England and of Riechelsdorf in 

 Germany (799:400). 



With changing environal life-conditions the above types 

 of fish evidently changed and evolved new though nearly 

 related genera from the Triassic on to the Mid-Jurassic 

 periods. These are Diplurus from the Trias of New Jersey 

 and Connecticut; Graphhiriis and Heptanema from the 

 Keuper beds, also Undina from the Lias; while Undina, 

 Libys and Coccoderma from Lower Kimmeridgean beds 

 carry the Crossopterygians on to mid-Jurassic times. 



In commenting on Huxley's review of the Coelacanths 

 (22/ : d 10, d, 12) Newberry writes (^5 : 338) : "Professor 

 Huxley has called attention to the very great resemblance, 

 and almost generic identity, of Coelacanthus, Undina^ and 

 Macropoma; and cites this succession of fishes — the in- 

 habitants of ages, to our comprehension, infinitely removed 

 from each other — as affording a striking example of what 

 he terms a 'persistent type.' " 



We may now inquire as to the distribution and en- 

 vironal relation of each of the above genera. Diplurus 

 longicaudatus was described by Newberry from specimens 

 secured at Boonton, N. J. and Durham, Conn. As more 

 recently discussed by Eastman, the age and position of these 

 beds seem to be "the summital portion of the middle Trias, 

 as developed in the Mediterranean region." {228:2^). 

 In both localities "certain layers of the shales are crowded 

 with fishes, a slab a yard square, carrying sometimes a half 

 dozen or more. Some of these are dismembered, con- 

 sisting of a shapeless aggregate of scales and bones, but 

 most are nearly perfect; and the number found at about 

 the same level with their perfection of preservation, 

 seem to show that the generation inhabiting that portion 

 of the Triassic basin at a certain time were some- 

 what suddenly killed and sunk to the bottom, where 

 they were soon covered with the accumulating sediment, and 

 were thus preserved. The layers of shale which contained 

 the largest number of fishes, are impregnated with bitumin- 

 ous matter, burning for a time when thrown into the fire, 

 and when struck with a hammer giving off a peculiar odor. 

 Similar fish beds are known to exist at Pompton, Plainfield, 



