STRUCTURES OF ARTHRODIRAN 135 
Arthrodirans. Sensory canals have been described chan- 
nelling the surface of the dermal plates of the dorsal side. 
In the body region of Coccosteus evidence of a lateral line 
occurs (Smith Woodward) in a white calcified band fossilized 
in the region of the space of the notochord. In this form, 
too, an endoskeletal plate is known, (Fig. 130, UV) occurring 
in the median line in the region of the vent, which must 
be regarded as “suggesting an internal element of support 
occurring in the vertical septum between the right and 
left halves of some paired organ (S. W.).” The character 
of the dermal investiture of the trunk has apparently 
not been described; it may therefore be of interest to 
note that the museum of Columbia College has recently 
acquired two of the hinder dorsal plates of Dinichthys 
which clearly indicate the presence of integument. The 
plates are covered by a crinkled epidermis, whose irregular 
surface traceries resemble the roughened finish of Turkey 
morocco. This leather-like surface is seen to have been 
continued over the margin of the plates along the side 
of the trunk; traces of scales or tubercles are altogether 
lacking, and its appearance suggests that it may have been 
degenerate in structure. 
Among Arthrodirans there occurs a series of most inter- 
estingly evolved forms; and it is found more and more 
evident that they, with other lung-fishes, may have repre- 
sented the dominant group in the Devonian period, as 
were the sharks in the Carboniferous, or as are the 
Teleosts in modern times. There were forms which, 
like Coccosteus, had eyes,at the notches of the head 
buckler; others, as Macropetalichthys, in which orbits 
were well centralized; some, like Dinichthys and Titan- 
ichthys, with the pineal foramen present; some with 
pectoral spines (?); some with elaborately sculptured derm 
