286 TRANSACTIONS OF THE [MAR. 15, 



only by name. Subsequent writers as Giebel, Bronn, McCoy, 

 and Morris have enumerated or redescribed these species and 

 have based upon irregular fragments of them descriptions of 

 supposed species of Coccosteus, Asterolepis and Platygnalhus. 

 The spines of Oracanthus are generall}' broadl}' triangular, com- 

 pressed, thin-walled, and the surface tuberculated ; hence they 

 were frequently found broken and the fragments were erroneously 

 referred to other genera. 



The bibliograph}^ of the genus has been recently worked out 

 with much care by Mr. J. W. Davis in his " Fossil Fishes of the 

 Carboniferous Limestone " (page 525) and he has given several 

 striking figures which illustrate the protean forms and singular 

 character of these spines, some of which were of enormous size. 

 One specimen figured by Davis is eight inches broad at the base 

 and must have been nearl}' a foot and a-half in length. Others 

 are broad triangles, two or three inches in length and in breadth 

 of base, very thin walled, mere shells in fact, which are much 

 compressed, distorted and broken. Such differences have sug- 

 gested to Mr. Davis that only a portion of these spines Avere dor- 

 sal and that others were set on different parts of the body, after 

 the manner of the spines of Climatius. 



In our own country the first species of Oracanthus was de- 

 scribed by Professor Joseph Leidy in the Journal of the Academ}- 

 of Natural Sciences of Philadelphia, Second Series, p. 161, pi. 16, 

 figs. 1-3 (1856). The t3'pe specimen of the species, which he named 

 0. vetustus, was obtained from some unknown locality in " Mis- 

 souri Territory " and was supposed to be from the Carboniferous 

 formation. It is about five inches in length, three inches broad 

 at base, very much compressed, its surfaces rather sparsel}- cov- 

 ered with tubercles, on one side arranged in transverse broken 

 lines, much as in 0. MiUeri, on the other side somewhat irregu- 

 larly scattered. 



In 1866 I described in the second volume of the Geological 

 Survey of Illinois (p. 117, PI. XII., fig. 3), a small broadly tri- 

 angular spine covered with scattered tubercles and having the 

 general character of Oracanthus, to which I gave the name of 

 0. pnigeus. This was from the Keokuk limestone. Similar 

 spines which occur in the Corniferous limestone of Ohio I had 

 previously described in the Bulletin of the National Institute, 

 1851, under the names of 0. fragilis, 0. granulatus, 0. abbrevi- 

 atus and O. multiseriatus. 



In 18V5 Mr. Orestes St. John took my Oracanthus pnigeus as 

 the type of a new genus to which he gave the name of Pnigea- 

 canthus (Geology of Illinois, Yol. YI., p. 480), giving to the 

 t^'pe species the name of P. deltoides. Later he added another 



