ON THE ANATOMY OF FISHES. 
105 
wards, and has thicker and more rigid walls than usual. In the smoothness of its 
inner surface, and in the total absence of all trace of secondary transverse septa, as 
well as in the narrow column-like shape of the primary transverse septum, the air- 
bladder very closely resembles that of Liocassis. A short tubular csecum is attached 
to the posterior end of the bladder, and has its cavity subdivided into two lateral canals 
by a corresponding backward prolongation of the longitudinal septum, which separates 
the two lateral compartments anteriorly. The two canals are distinct from each other, 
but communicate with their respective lateral chambers in front. In the general 
structure of the walls of the anterior chamber, and in the relations and attachments 
of their principal sheets of fibres to fixed parts of the skeleton and to the tripodes, 
Bagroides exhibits no perceptible difference from Macrones. We have described the 
walls of the air-bladder as being thicker and more rigid than usual , but this statement 
does not accurately apply to the antero-lateral regions of the anterior chamber, for 
there the walls are extremely thin over definitely circumscribed areas exactly 
co-extensive with the post-temporal plates. In each area the wall of the bladder 
appears to be formed mainly, if not exclusively, by the vertically disposed fibres of 
the inner stratum of the tunica externa, with the addition of the extremely thin 
tunica interna. Both areas bulge forwards into the concavities of their respective 
post-temporal plates. 
The Weberian ossicles are very similar to those of 3£acrones, except that the heel- 
like process of the tripus is of unusual length, being, in fact, as long as the posterior 
or inwardly-curved segment of the crescentic process. The intercalarium has tolerably 
stout ascending and horizontal processes. 
Rita crucigera. 
This species, so remarkable for the enormous size of its pectoral and dorsal spines, 
which in a specimen less than twelve inches long were four and a half and three 
inches in length, respectively, and proportionally massive, vei’y closely resembles 
Pseudohagrus hrachysoma in most of the osteological details with which we are now 
concerned. 
The decurved anterior division of the transverse process of the fourth vertebra is 
somewhat shorter than usual but very massive. Its distal half is flattened from 
before backwards, and, anteriorly, is firmly applied to the relatively slender inferior 
limb of the post-temporal, to the entire exclusion of the latter from contact with any 
portion of the anterior wall of the air-bladder. The distal portion of the process is 
not produced into a crescentic prolongation but somewhat abruptly ceases at the 
point where it forms the inner margin of the articular groove for the clavicle. The 
altogether exceptional thickness of these processes is obviously correlated with the 
equally exceptional development of the pectoral spines and the girdle which supports 
them. The superficial o.ssifications investing the complex and fifth vertebral centra 
MDCCCXCIII. — B. j> 
