"VYELLBURX : OX THE GEXUS MEGALICHTHYS, AGASSIZ. 
59 
The greater number of the dermal rays arise from the lower 
aspect of the body prolongation, whilst the apex is formed by 
those arising from the dorsal side of the axis. (This is clearly 
shown in a specimen in Owens College Museum.) (PI. XVII., 
Fig. H.) The posterior margin of the fin slopes obliquely upwards 
and backwards, and the dermal rays are articulated, covered with 
ganoine, increased by dichotomisation distally, the uppermost ones 
are the most robust and the proximal part of the upper border 
of the fin is strengthened by well-marked "ridge scales," which 
are continuous with those on the dorsal ridge of body. 
Internal Skeleton. (PL XYIL, Fig. F.) The specimen of 
Megalichthys Ilihherti Ag., Xo. 3(S,007, already mentioned, shows 
that the internal structure was of a similar nature to that of 
TristichopteriLS alatus Egerton,"^ viz., the more anterior dermal rays 
are supported on a series of "hour-glass" shaped interapophyscal 
osselets, each osselet having several rays opposed to their distal 
end, their proximal ends uniting with the distal extremities of 
elongated and thickened neural and hoemal spines of the vertebral 
column. More posteriorly the dermal rays seem to abut on the 
vertebral axis. 
Vertebral Column.— -In the Andersonian Museum, Glasgow, 
there is a slab w^hich contains, besides the upper surface of the 
head, a good display of the vertebral column. About fifty 
vertebrae are shown, of which the anterior are the shortest and 
broadest, the caudal being the longer and narrower. 
The notochord is partially persistent, the cartilages of the 
arches are superficially calcified, there are robust ring-shaped 
vertebrae, and several specimens (in the Science and Art Museum, 
Edinburgh ; British Museum ; in the Author's Collection, &c.) 
show well-marked neural spines, which have a cylindrical shaft, 
articular head, and are somewhat flattened distally. Haemal 
.spines are also shown in the caudal region in several specimens. 
* See Mem. Geol. Survey (Figures and descriptions organic remains), 
Dec. X, PI. 4 and 5, pp. 50-53. 
