ON THE ANATOMY OF FISHES. 
107 
Of the Weberian ossicles, the tripus and the scaphium are for the most part 
perfectly normal ; the intercalarium, however, has neither ascending nor horizontal 
processes, and, in fact, is represented only by a small nodule of bone imbedded in the 
middle of the interossicular ligament. The tripus {tr.c.) has no heel-like process, and 
its anterior extremity is somewhat thickened for the attachment of the stout 
interossicular ligament. In correlation with the exceptional thickness of the walls 
of the air-bladder the crescentic process, and its ventral ridge, are more stoutly 
developed than in most of the preceding types. 
Akysis variegatus. 
We have only been able to examine solitary examples of the two rare species, 
Akysis variegat us and Acrochordonichthys pleurostigma, and it unfortunately happened 
that both specimens were too badly preserved to admit of our results being otherwise 
than incomplete. We regret this the more because it is obvious that in these species 
both the air-bladder and the skeleton, and especially the former, differ considerably 
from the more normal types of those structures that we have so far described. As 
our specimen of Akysis was slightly the better preserved of the two, we shall deal with 
it first. 
Tlie centrum of the first vertebra is a thin discoidal bone completely excluded from 
view on the ventral surface by the forward extension of the superficial ossifications. 
The complex and fifth vertebrae are rigidly connected together, and as firmly united 
to the skull by the superficial ossifications, which not only invest the lateral surfaces 
of their centra, but also extend forwards on to the ventral surface of the body of the 
first vertebra, and even slightly overlap the basioccipital. The sixth vertebra is quite 
free, and its transverse processes carry the first pair of ribs. The spine of the third 
vertebra is represented by a thin lamina of bone, the dorsal margin of which slopes 
downwards towards the skull, and articulates by a serrated suture with a descending 
process derived from the supraoccipital spine. The spinous process of the fourth 
vertebra is exceptionally massive, and cleft distally for the support of the first 
two interspinous bones of the dorsal fin. The transverse process of the fourth vertebra 
is not only greatly expanded, but its anterior and posterior margins are somewhat 
decurved so as to form the anterior and posterior boundaries of a shallow concave 
recess on the ventral side of the process (fig. 29, t.pA). The anterior margin is much 
thicker and more strongly decurved than the posterior, especially towards its outer 
extremity, where, in addition, it curves slightly backwards. The remainder of tlie 
process is comparatively thin and somewhat triangular in shape, with the apex 
directed outwards. The decurved anterior portion, and the thin triangular lamina 
respectively represent the usual anterior and posterior divisions into which this trans- 
verse process is normally divided. The corresponding proce.ss of the fifth vertebra is 
more strongly developed than its successors, with a slight forward inclination and a 
V 2 
