152 IOWA GEOLOGICAL SURVEY 



name of Hoplonchus parvulus. According to Smith Woodward, 

 the so-called Homacanthus gracilis of Whiteaves, from the 

 Lower Devonian of Campbellton, New Brunswick, may belong 

 to an Acanthodian resembling Climatius. 



Formation and locality. Chemung Group; Warren, Pennsyl- 

 vania. 



Homacanthus delicatulus Eastman. 



1903. Homacanthus delicatulus C. R. Eastman, Bull. Mus. Comp. Zool. 39, 

 p. 218, pi. 3, fig. 28, pi. 5, fig. 59. 



Spines very diminutive, erect, deeply inserted; base of ex- 

 serted portion relatively broad, distal extremity acute, sides 

 ornamented with not more than five or six straight longitudinal 

 costae. 



The holotype is a unique specimen from the Kinderhook lime- 

 stone of LeGrand, Iowa, where it occurs in company with a num- 

 ber of typically Mississippian species, though probably itself rep- 

 resenting a survival of the Upper Devonian fish-fauna. Ap- 

 pearances suggest that it does not belong to a young individual, 

 but to an adult of very small, even dwarfish proportions. 



Formation and locality. Kinderhook limestone; LeGrand, 

 Iowa. 



Genus CTENac*NTHUS Agassiz. 



Spines robust, those of the first dorsal fin often attaining a 

 large size, laterally compressed; sides of exserted portion orna- 

 mented with longitudinal ridges, usually crenulated or denticu- 

 lated, rarely smooth; posterior face flat or concave, with a series 

 of small denticles along each margin. Spines of the second dorsal 

 fin characterized by their abbreviate, stumpy proportions and 

 oblique angle of insertion in the integument; ornamentation as 

 in the longer, more gracefully curved ones of anterior dorsal fin. 



It is certain that spines of this character were common to 

 more than one genus of Palaeozoic sharks. Eeference has al- 

 ready been made to the occurrence of spines indistinguishable 

 from those of this genus in Cladoselache, and Newberry was 

 strongly inclined to believe, owing to the discovery of asso- 

 ciated fragments from the Ohio Waverly, that the spines called 



