258 IOWA GEOLOGICAL SURVEY 



within. Fins of moderate size, consisting of delicate rays, dis- 

 tally bifurcated, with an anterior series of slender fulcra; prin- 

 cipal rays of pectoral fin unarticulated except near their distal 

 extremity. Dorsal and anal fins triangular, partly or com- 

 pletely opposed ; upper caudal lobe slender, and caudal fin deeply 

 forked, unsymmetrical. Scales large or of moderate size, more 

 or less delicately sculptured; ridge-scales in advance of dorsal 

 fin much enlarged. 



This genus was established by Dr. Traquair in 1877 to include 

 several earlier described Palseoniscid species, typified by P. or- 

 natissimus Agassiz, from the Scottish Lower Carboniferous. 

 The characters of generic importance displayed by this species 

 and by the closely related P. carinatus Agassiz, and the form 

 designated (but not described) by Professor J. Young as "P. 

 wardi" , are stated by the original author to be as follows: 



"The body is comparatively slender; the suspensorium is 

 very oblique; the jaws are armed with a row of incurved conical 

 laniaries, outside of which there is a series of smaller teeth ; the 

 principal rays of the pectoral fin are, as in Pygopterus and Oxy- 

 gnathus, unarticulated till towards their terminations ; the 

 caudal body-prolongation is comparatively delicate. There are, 

 besides these, several other new species from British Carbon- 

 iferous strata referable to this type, the description of which I 

 hope soon to be able to overtake; in some of these the scales 

 are nearly smooth, as in R. carinatus, in others elaborately or- 

 namented."* 



Rhadinichthys devonicus (Clarke). 

 (Text-figure 38) 



1885. Paloeoniscus devonicus J. M. Clarke, Bull. U. S. Geol. Surv. no. 16, pp. 



20, 41, pi. 1, figs. 2-6. 

 1889. Palceoniscus devonicus J. P. Lesley, Dictionary of the fossils of Penn., 



etc: Geol. Surv. Penn., Rept. P4, vol. 1, p. 585, figures. 

 1907. Rhadinichthys devonicus C. R. Eastman, Mem. N. Y. State Mus. 10, 



p. 171. 

 1907. Rhadinichthys devonicus D. D. Luther, 59th Ann. Rept. N. Y. State 



Mus. 2, p. 46. 



A gracefully formed species with slender trunk, attaining a 

 length of at least 12 cm and possibly longer. Headbones deli- 



*Traquair, R. H., On the Agassizian Genera Amblypterus, Palseoniscus, etc. 

 Quar. Journ. Geol. Soc. (1877), 33, p. 559. 



