The Dipneusti and Crossopterygii 295 



will be met with in greater abundance than anywhere in the 

 Corniferous Limestone" he mistakes the environal relation 

 of all of the rocks, as already indicated (p. 129). 



In close succession, however, to the above appeared those 

 increasingly gigantic but related forms which, from North 

 Europe, have been described as Homosteus and Heterost- 

 eus. From there as well as from the Delaware limestone 

 strata of North America evolved others that have been 

 named MacropetaUchthys. From the Delaware strata also, 

 still others reached a climax of size, of cumbrous defensive 

 specialization, and of relative abundance, so that they have 

 been well named Dinichthys and Titankhthys. In some 

 species of the last genus, the head must have been about 

 three feet across, and the entire animal from ten to twelve 

 feet in length. 



Speaking of Coccosteus and Dinichthys^ Eastman says 

 in the Journal of Geology (8.p.i88) "The two genera are 

 most intimately related, and though their terminal members 

 are sufficiently well characterized, they are connected by 

 insensible gradations. The typical species of Dinichthys 

 represent unquestionably a later and more advanced stage 

 of specialization than that with which we are familiar in 

 Coccosteus decipiens for example. But between these ex- 

 tremes lies a host of intermediate forms. Evidence of 

 specialization in forms like D. herzeri, D. terreUi etc. is 

 strikingly apparent." The subject is more fully discussed 

 by him also in a later work {225: 1 18-139). 



As to the distribution, the European genera are all 

 found in rocks that during the past quarter century have 

 been accepted as freshwater in origin. The eastern Ameri- 

 can genera and species range from the Delaware up into 

 the highest' division or Cleveland shale, and were all of 

 freshwater habitat. That considerable expanses of more 

 or less connected freshwater — ^^either lakes, swamps, or 

 rivers — may have flooded large tracts of country at times, 

 and so gave ample opportunity for growth, variations, and 

 increasingly wide distribution of Dinichthys, is clearly 

 proved. Thus D. pustulosus and D. tuherciilatiis have been 

 recorded from western New York, southward to Kentucky, 

 and westward to Iowa, Illinois, and Wisconsin. This need 



