190 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



advance of the pelvic pair ; second dorsal midway between the anterior dorsal 

 and principal caudal ; the latter comprising nine stout rays above and below. 

 Scale structure and ornamentation of head-bones not observed. 



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 de- 

 ficient in preservation. They agree in having a narrow, gradually tapering 

 body, which terminates in an equilobate caudal fin, with indications that the 

 axis was prolonged into a supplementary caudal. The anterior dorsal and 

 caudal, owing to their firmer attachment, are preserved in nearly all specimens, 

 but the remaining fins have in most cases become lost. The first dorsal has 

 usually seven or eight stout rays, and is situated near the middle of the trunk. 

 Ten long, hollow rays are to be counted in the single specimen di.splaying 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 squamation 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. 



Formation and Locality. — Coal Measures; Mazon Creek, Illinois. 



ACTINOPTERYGII. 



PALAEONISCIDAE. 



ELONICHTHYS Giebel. 



Two closely related species are already known from Mazon Creek, E. pcl- 

 tigerus Newberry, and E. hypsilepis Hay. A study of the type specimen of 

 Newberry and Worthen's so-called " AmhlyjHerus nmcropterus," now preserved 

 in the Yale Museum, leaves no doubt that this is only a mutilated individual 

 of E.j)eltigerus. The type of Rhadinichthys gracilis (Newberry and Worthen) 

 is also preserved in the Yale Museum. 



Blonichthys perpennatus Eastman. 



(Plate 5, Pig. 49.) 



1902. Elonichthijs perpennatus C. R. Eastn)an, Journ. Geol., Vol. X., p. 539, Text- 

 fig. 4. 



Type. — Complete individual; Museum of Comparative Zoology. 



A very small species, having a total length of about 2.5 cm. of which the 

 head occupies a little less than one fourth. Fins extremely well developed, 

 the pectorals unusually long, and anal much extended; fulcra minute. Scales 

 relatively small, obliquely striated; dorsal ridge-scales enlarged. 



