Davis—On the Fossil Fishes of the Chalk of Mount Lebanon. 503 
their point of attachment with the caudal rays. A long series of spinous and 
interspinous bones support the dorsal fin; and anteriorly the two are connected 
by free rods of bone, the latter overwrapping the free ends of the spinous and 
interspinous processes. Dorsal fin very large. Anal about half the length of the 
dorsal. 
The heterocercal arrangement of the termination of the spinal column and the 
hzmapophyses supporting the caudal fin greatly resemble those of the ganoid 
Lepidosteus. The constitution of the dorsal and anal fins do not share the 
resemblance. There is no evidence of scales. It is considered advisable to place 
the genus provisionally amongst the Ganoids, and await the advent of more 
perfect specimens to prove whether the determination is the correct one. 
Spathiurus dorsalis, Davis. 
(Bl xxxyvi., tig. 1.) 
The specimen, which is unique, exhibits only the caudal portion of the fish. 
The slab is broken diagonally across the body. The entire length preserved is 
9 inches; from the base of the tail 7-0 inches of the dorsal surface is preserved, 
but only 2°5 inches of the ventral. The part of the spinal column which remains 
is 5 inches in length, comprising thirty-three vertebre. The vertebre are 
0-3 inch in height and 0:2 inch in length. They decrease in size towards the 
caudal extremity. The latter is very decidedly heterocercal. The neurapophyses 
are strongly attached, one to each vertebra, curve gently backwards, and extend 
midway towards the dorsal margin of the fish. Interneural spines, interlocking 
with the apophyses, extend to and support the rays of the dorsal fin; they are 
straight and widely expanded for attachment. Commencing at about the 
twenty-fourth vertebra from the tail, a series of slightly-bent, rod-like bones 
extend intermediately between the spinous and interspinous bones, serving to 
support and combine the action of the two. The hemal and interhemal bones 
are similar to the neural. 
The dorsal fin extends from the base of the tail 6:0 inches in length; it is 
large, supported by strong rays, expanded at the base where connected with the 
interspinous processes; the basal portion forms a solid hollow tube, averaging 
about 0°5 inch in length; beyond it becomes articulated, and by dichotomization 
is much divided at the distal extremity. The fin comprises forty-four rays. The 
anterior ones are apparently of the same character as those behind, but may have 
been spinous. It has unfortunately happened that all except a short piece of the 
base has been lost. The rays near the middle of the length of the fin are 1:0 inch 
in length. The anal fin is not preserved. ‘The base of the anterior rays and their 
connection with the interspinous processes is exhibited; they are strong and bent 
3Z 2 
