237 
contained nearly four times in the total length of the fish. The 
outer layer of the head-bones is much destroyed, and no tuber- 
cular ornament can be seen. Very stout, closely-arranged teeth 
are observed in the mandible. The operculum is somewhat 
deeper than broad, and the preoperculum exhibits a wide expan- 
sion ; the width of the operculum equals that of the lower 
suborbital plate. The paired fins, the anal, and the lower lobe 
of the caudal fin are too imperfect to show the fulcra ; but these are 
observed on the front border of the dorsal, and the upper lobe of 
the caudal fin. The pelvic fins arise almost exactly opposite the 
origin of the dorsal, and are much nearer to the anal than to the 
pectorals. The dorsal fin arises in advance of the middle point 
of the back, and comprises about 17 rays; the anal fin is twice 
as far from the caudal fin as from the pelvic pair ; the caudal fin 
is not very deeply cleft. There are the usual enlarged post- 
clavicular scales ; and the exposed area of the middle flank-scales. 
is slightly deeper than broad. All the scales are smooth, only 
very feeble traces of crimping at their hinder border being 
observable in the lower part of the abdominal region. The 
thicker scales on the atrophied upper caudal lobe have already 
been mentioned. The “lateral line” is marked only by notches 
in the scales. The total length of the fish is about 0°38 m. 
PACHYCORMUS. 
It is noteworthy that among the ganoid fishes of the Mesozoic 
period, there are many forms which curiously mimic in outward 
aspect certain groups of modern bony fishes. Some have great 
pectoral fins and might be called “flying fishes ;’ others are 
armoured much like the ‘“ box fishes ;’ some are ribbon-shaped 
and with elongated snout like a modern Belone; others are 
almost eel-shaped. A detailed examination of the skeleton, 
however, shows that these are mere parallel forms of life and are 
not intimately related to the existing fishes which they mimic. 
They obviously belong to a much lower grade of their class, and 
