164 NEW YORK STATE MUSEUM 



On the other hand, Dipterine remains are present in astonishing abun- 

 dance and considerable variety in the western Neodevonic, specially the 

 State Quarry beds of Johnson county, Iowa. A number of representative 

 forms, some of them belonging to still undescribed species, are shown in 

 plate 2, figure i, and plate 4, figures 2, 7, 8, 12, 15 and 16. It is to be 

 regretted that no portions of the skeleton, other than the dentition, have 

 yet been brought to light from this region. 



Subclass TELEOSTOMI 

 The great group of fishes commonly known under the designations of 

 Ganoids and Teleosts and first recognized by Owen as a single subclass, 

 Teleostomi, makes its appearance in the Lower Devonic, but does not 

 really become significant until the Carbonic. The Crossopterygian order, 

 which predominates during the Devonic, is somewhat abundantly repre- 

 sented toward the close of that system in this country; but except in 

 Canada, all the remains are extremely fragmentary, consisting of detached 

 scales, teeth, plates, and in two or three instances of imperfectly preserved 

 skeletons. The most important American genera are Holoptychius, Saurip- 

 terus, Onychodus and Eusthenopteron, but of these the last named alone has 

 been found in a state bordering upon completeness. Nevertheless, it is 

 possible to frame a tolerably accurate conception of the remaining genera 

 through comparison of their characteristic parts with the admirably pre- 

 served skeletons of their foreign representatives, especially those from the 

 Scottish Old Red sandstone. In this way the detached head plates and 

 bones of the shoulder girdle belonging to Onychodus, for instance, acquire 

 much greater significance than would otherwise be possible. The osteology 

 of various typical members of the Crossopterygian order is now quite satisfac- 

 torily known, as the result especially of the researches of Pander,' Huxley^ 



' Pander, C. H. Ueber die Saurodipterinen, Dendrodonten, Glyptolepiden, und 

 Cheirolepiden des devonischen Systems. St Petersburg i860. 



^ Huxley, T. H. Illustrations of the Structure of the Crossopterygian Ganoids. 

 Geol. Sur. Mem. United Kingdom 1866. Reprinted also in the Scient. Mem. of T. H. 

 Huxley, Suppl. volume, 1903. 



