CA RBONIFER O US FISH-FA UNA 539 



This species is represented by ten specimens in the Yale, and 

 one in the Harvard Museum, most of them being only about 

 3 cm long, and very deficient in preservation. They agree in 

 having a narrow, gradually tapering body, which terminates in 

 an equilobate caudal fin, with indications that the axis was pro- 

 longed into a supplementary 

 caudal. The first dorsal and 

 caudal, owing to their 

 stronger attachment, are pres- 

 ent in nearly all specimens, 

 but the remaining fins have 



in most cases become de- Fig. $. — Elonichthys perpennatus, sp. 



Stroyed. The first dorsal has n ° V - Coal-measures, Mazon Creek, 111. 



Complete individual, the distal portions of 

 usually seven or eight stout med i a n fins not fully shown. Xf. 

 rays, and is situated near the 



middle of the trunk. Ten long, hollow rays are to be counted 

 in the single specimen displaying the posterior dorsal, and nine 

 above and below in the symmetrical caudal. The neural and 

 haemal spines are very long in the abdominal and caudal 

 regions. The ossifications of the axial skeleton are continued 

 nearly to the termination of the principal caudal. The squama- 

 tion must have been exceedingly delicate, as no indications of 

 scales are to be observed in any of the specimens, nor do any of 

 them have the cranial elements satisfactorily preserved. 



GENUS ELONICHTHYS, GIEBEL. 



Two closely related species are already known from Mazon 

 Creek, E. peltigerus Newberry, and E. hypsilepis Hay. A study 

 of the type-specimen of Newberry and Worthen's so-called 

 " Amblypterus macropterus," now preserved in the Yale museum, 

 leaves no doubt that this is only a mutilated individual of E. 

 peltigerus. The type of the following new species is preserved in 

 the Museum of Comparative Zoology. 



Elonichthys perpennatus, sp. nov. 



Description. — A very small species, having a total length of about 2.5 cra , 

 of which the head occupies a little less than one-fourth. Fins extremely well 



