102 
PROFESSORS T. W. BRIDGE AND A. C. HADDON 
grooved on its posterior face, and the groove receives the vertical ridge of fibrous tissue 
which imperfectly separates the two cavities. 
Bagrus hayad. 
In the structure of the air-bladder and in the general details of its osteology this 
African Siluroid differs in no essential respect from Macrones nemurus. Relatively 
to the size of the body the air-bladder is somewhat smaller than in the latter species, 
and, with the exception of a single short but stout secondary transverse septum in 
each of its lateral compartments, has smooth walls and undivided cavities. The 
walls of the bladder are moderately thick, but somewhat thinner in the lateral and 
antero-lateral regions than elsewhere. The tripus has no heel-like process, and the 
intei’calarium has a well -developed ascending process in addition to a horizontal one. 
Bagrus docmac. 
In a skeleton of this species in the British Museum we noticed that the post- 
temporal plates were incompletely ossified, a deep cleft extending inwards from their 
outer margins. 
Chrysichthys macrops. 
In a skeleton of this Siluroid in the British Museum collection the anterior margin 
of each of the transverse processes of the fourth vertebrae was bent sharply down- 
wards so as to form a vertical, transversely disposed plate which must have excluded 
the post-temporal plate from contact with the anterior Avail of the air-bladder. 
Bseudohagrus hrachysoma. 
In this Siluroid there are several noteworthy peculiarities of the skeleton in which 
it differs from most of the preceding species. 
The stem and inferior limb of the post-temporal (fig. 26 , pt.s., pt.i.) are no way 
modified to form the post-temporal plate which is so characteristic of the various 
species of Macrones and Bagrus. On the contrary the stem is vertically cleft into 
an inner and an outer process, and the cleft Avith its groove-like prolongation forms an 
articular cavity {cl.s.) for the proximal extremity of the clavicle, the latter being 
retained in position by strong ligamentous fibres Avhich convert the groove into a 
tubular socket. The transverse process of the fourth A’^ertebra is so deeply cleft that 
its divergent anterior and posterior divisions [t.p.^a., are but slightly united at 
their roots, and would resemble normal transverse processes but for their greater 
length and thickness. The posterior division [t.'p.^p.) is directed obliquely backAvards, 
and has its root connected by a thin lamina of bone with the corresponding portion of 
