20 
]■ arrows ; suboperculimi large, but smaller than the trapezoidal o})erculnm, 
from which it is divided by an oblique suture. Yertel)iac in the form of 
mneh-constrieted cylinders, wdth little or no secondary ossiheation ; inter- 
museiilar bones feebly developed. Eins consisting of delicate, diehotomonsly 
branching rays ; fulcra absent. Pelvic fins relatively large ; dorsal tin about 
as long as deep, opposed to the pelvic pair or to the space between the latter 
and the anal ; anal small, not extended ; caudal deeply forked. Seales very 
thin, cycloidal, and the ex])oscd portion invested Avith continuous, smooth 
enamel ; no (mlarged or thickened ridge-seales. 
Osteology of the (Jeniis. — No satisfactory concise synopsis of all the 
principal ostcologieal characters of Leptolepis appears to have hitherto been 
published. The beautiful impressions of the skeleton in the now Australian 
collection may therefore be utilized in attempting an amended and amplified 
description. 
The external bones and scales are covered with a very thin layer of 
ganoine, always smooth or only feebly rugose. The cranial roof is flattened 
in the middle, abru])tly truncated behind, and very narrow betAveen the 
orbits ; the parietals are very small, and the suture betAveeu the much- 
elongated frontals is Avavy. The parasphenoid is delicate. There is a series 
of large suborbital l)ones, and the sensory canal traversing them exhibits a 
series of short branches radiating doAviiAvards. The sclerotic ring is ossified. 
I'he })rcmaxilia is minute, and the long curved maxilla, haAung minute teeth 
on its convex oral margin, is contracted, though comparatively robust at its 
loose anterior articulation. There ari' also two elongated supramaxillary 
bones, deeply overlapping the maxilla. The mandible is deep in the middle, 
tapering at either end, and consists almost entirely (if not entirely) of tAA'o 
elements. The robust dentary bone is remarkable for tlie deep coronoid 
process rising nearest its anterior end ; behind, and partly above it, is the 
large laminar articular element. The ceratohyal has the ordinary hour-glass 
form, but is notcAVorthy for the extension of a supplementary, delicate, 
straight rod of bone between its extremities on the up|)er side. The oper- 
cular apparatus is complete, and the sensory canal upon the prcoperculnm 
exhil)its radiating branches resembling those of the snborbital line. The 
])ranchiostegal rays on tlie short cpihyal arc broad and imbricating, Avliih' 
tliose supported by the ceratohyal are spaced and delicate ; and there is no 
trace of a gular plate in any sjAecinien examined by the present ATiter. 
One i>air of large supratemporal plates occurs behind tlie occiput, and 
the Avliole of the trunk is covered Avitli imlndcating cycloidal scales, Avhich 
