ON thf: anatomy of fishes. 
149 
pointed process, is firmly united by suture to the anterior margin of the transverse 
process of the fifth vertebra. Proximally, as well as distally, the anterior and posterior 
walls of the bony semicylinder contract somewhat, and hence the enclosed recess 
becomes oval in shape in accordance with the contour of the contained air-sac. As in 
Bagarius the roof of the recess becomes so thin over a well-defined oval area as to be 
almost transparent. Two small foramma perforate the thick flat root of the process, 
and serve for the transmission of the rami ventrales of the fourth and fifth spinal 
nerves (fig. 55, sp.n.^, sp.n}). The transverse process of the fifth vertebra (figs. 55 
and 56, tp.^) is unusually long and stout, with a free distal extremity, which is 
slightly recurved, and an anterior margin suturally articulated with the posterior 
margin of tire preceding process. The origin of the process from the centrum, instead 
of from the neural arch like its predecessor, causes it to occupy a slightly more ventral 
position ; and, although not actually in contact with the air-bladder, it nevertheless 
helps to deepen the recess in which that organ is lodged. Its root is perforated for 
the passage of the ventral division of the sixth spinal nerve (fig. 55, sp.n.^). 
The superficial ossifications are but feebly developed in Glyptosternum. Tlie sides 
of the centra of the first, the complex, and the fifth vertebrae are apparently somewhat 
thickened by superficial ossified deposit, but not continuously so, inasmuch as the inter- 
vertebral sutures are very evident, both on the lateral and ventral surfaces, and there 
is absolutely no trace of an aortic groove (fig. 55). On each of the ventro -lateral 
margins of the complex centrum there is a well-marked ventral ridge, and from this 
ridge, as in Bagarius, a thin, slender ventral process extends horizontally outwards 
to a point a little beyond, and ventrad to, the commencement of the oval recess 
enclosed by the modified transverse process of the fourth vertebra, and there termi- 
nates in a flattened and slightly expanded extremity (fig. 55, v.p.). At the junction 
of the flat root of the transverse process, with its more cylindrical distal portion, a 
slender spicule of bone id.l.) grows downwards, and at its ventral extremity beccnnes 
firmly applied, if not actually anchylosed, to the dorsal or inner surface of the distal 
end of the ventral process. When the two processes meet, the vertical process gives 
off a slender prolongation, which passes horizontally forwards and a little downwards 
to articulate with a projection furnished by the frfee inner extremity of the decurved 
anterior margin of the transverse process (see left side in fig. 55, also in fig. 57). We 
have no difficulty in identifying the horizontally-disposed ventral process of Glypto- 
sternum with the similarly situated process of Bagarius, and it is equally evident 
that the vertical process which meets its distal extremity is the equivalent of the 
dorsal lamina of other Siluroids. That the dorsal lamina in Glyptosternum does not 
reach the complex centrum is certainly peculiar, but it may be noted that its vertical 
and horizontal processes retain their normal relations to the posterior cardinal vein 
and the mesonephros, in that the latter structures pass between the former and 
the h teral surface of the complex centrum. The failure of the dorsal lamina to reach 
