ON THE ANATOMY OF FISHES. 
173 
From their thinness and partial translucency the lateral and cutaneous areas 
(fig. 69, l.c.a.) are readily noticed in an external view of the Fish. Each area is 
bounded by, and adherent to, the post-temporal in front, the upper lip of the mouth 
of the osseous funnel above, and the lower lip of the funnel and the distal 
extremity of the transverse process of the fifth vertebra below. The lateral line 
canal {l.l.c.), with its protective tubular ossicles, crosses the upper margin of each 
area. 
Gkoup Malapteruhina. 
Malapterurus electi'iciis. 
G. St. Hilaire and Johannes Muller have referred to the air-bladder of this 
species. The former in his work on Egypt (35) gives a brief description of the external 
appearance of the organ which he also figures {loc. cit., Plate 12, fig. 4), while Miiller 
(28) simply includes Malapterurus among those Siluridse in which he had found an 
“elastic-spring” apparatus. Sorensen (36) has also figured the air-bladder, and in 
a recent paper (37) has described the mode of formation of the terminal plates of the 
“ elastic springs.” The promise of an anatomical investigation of Malapterurus by 
the late Professor Goodsir, referred to by Murray in his “ Remarks on the Natural 
History of Electric Fishes ” (28a), was fulfilled by Dr. Cleland (6a). 
The complex and fifth vertebrse are firmly connected together by investing super- 
ficial ossifications, as well as by the partial anchylosis of them neural arches and 
spines. Their centra are nearly equal in size, that belonging to the complex vertebra 
being but a trifle the longer of the two. The body of the first vertebra is very feebly 
developed in the form of a thin, wafer-like bone, wedged in between the basioccipital 
and complex centrum. In correlation with the absence of a dorsal fin the anterior 
neural spines are very short, and none are cleft for the support of interspinous bones. 
The arch and short spine of the third vertebra (fig. 72, n.s.^) are inclined forwards 
towards the snpraoccipital and exoccipitals, and connected therewith by a considerable 
amount of intercalated cartilage. The spine of the fourth vertebra is almost obsolete, 
and that of the fifth {n.s}) is but feebly developed, serving merely to buttress the much 
stronger spine of the sixth vertebra. The sixth vertebra itself is quite free, both as 
regards its centrum, arch, and spine. 
Each of the transverse processes of the fourth vertebra is cleft to its root into 
distinct anterior and posterior divisions (fig. 72). The former [t.p.hi.) has an extremely 
thin but highly elastic root, which grows out from the neural arch of the complex 
vertebra, and at its origin is slightly oblique in a direction from below upwards and 
backwards. x\fter a slight ventral flexure the elastic root expands at its distal 
extremity into a very thin, transversely-disposed oval plate of extremely brittle bone, 
which is closely applied to the outer portion of the anterior wall of the air-bladder 
rather than to the antero-lateral region, the two surfaces of the plate looking 
