EASTMAN : CARBONIFEROUS FISHES FROM THE CENTRAL WEST. 207 

 Physonemus hamus-piscatorius, sp. nov. 



(Plate 5, Figs. 45, 46.) 



Type. — Exserted portions of spines ; Museum of Comparative Zoology. 



Small hook-shaped spines, circular in cross-section, traversed by a small 

 central pulp-cavity, and maintaining a nearly uniform diameter for the greater 

 part of their length. External surface smooth or slightly roughened but not 

 tuberculated, and no denticles present on either side. Inserted portion not 

 observed. 



The peculiar unciform spines shown in Plate 5, Figs. 45 and 46, from the 

 Kinderhook limestone of Iowa, are the only examples at present known of this 

 species. Both specimens are slightly abraded and afford no clue as to the 

 nature of the inserted portion. The larger one is also fractured longitudinally 

 for a considerable distance in such manner as to expose the tubular pulp- 

 cavity, which in contrast to most species occupies a central position. The 

 most striking differences displayed by the present form, however, are its cir- 

 cular cross-section and almost total absence of ornamentation. A small spine 

 from the St. Louis limestone described by Messrs. St. .lohn and Worthen as 

 Physonemiis falcatus, but which is probably the young of P. arcuatm, ap- 

 proaches the present form in its general outline, but differs notably in cross- 

 section and other features. There is no reason to suppose that these spines 

 are abnormally recurved, but on the contrary they may be looked upon as at 

 once the most primitive, as they are also the earliest known representatives of 

 Physonemus. 



Formation and Locality. — Kinderhook limestone ; Burlington, Iowa. 



Physonemus pandatus, sp. nov. 



(Plate 5, Fig. 44.) 



Type. — Complete spine ; Museum of Comparative Zoology. 



Small, narrow, laterally compressed spines, the exserted portion erect and 

 scarcely tapering for two thirds of its length, then becoming suddenly bent, 

 more or less at right angles, but not decurved. External surface apparently 

 unornamented, and denticles absent along the concave margin. 



The unique example upon which this species is founded exhibits the whole 

 of the exserted portion, and is broken off at the expanded base, the inference 

 being that it was buried only to a slight extent in the integument. It is dis- 

 tinguished from the preceding species principally by its great lateral com- 

 pression, and in its abrupt flexure without l)eing curved downward toward the 

 distal extremity. No traces are to be observed of superficial ornamentation, 

 nor of denticles along the concave margin. This .species, like the last, may be 

 looked upon as a primitive forerunner of the group typified by P. arcuatu,% 

 immediately to be considered. 



Formation and Locality. — Kinderhook limestone ; Burlington. Iowa. 



