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 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 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, -Lllinois. 
ACTINOPTERYGII. 
PALAEONISCIDAE. 
ELONICHTHYS GIzset. 
Two closely related species are already known from Mazon Creek, £. pel- 
tigerus Newberry, and EL. hypsileprs 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 EH. peltigerus. The type of Rhadinichthys gracilis (Newberry and Worthen) 
is also preserved in the Yale Museum. 
Elonichthys perpennatus Eastman. 
(Plate 5, Fig. 49.) 
1902. Elonichthys perpennatus C. R. Eastman, 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. 
a! 
