ON THE ANATOMY OF FISHES. 
73 
It will be obvious that the modified transverse processes of the fourth and fifth 
vertebrae combine to form on each side of the complex and fifth vertebrae an almost 
continuous bony plate, with a smooth and slightly concave ventral surface and a 
strongly deflected anterior margin, which is adapted and intimately applied to the 
convex dorsal and anterior walls of the anterior third of the air-bladder. 
The transverse processes of the sixth vertebra are normal except for the slight 
coalescence of their roots with the corresponding processes of the fifth vertebra. 
Their origin is from the centrum and not from the neural arch, and their distal 
extremities carry the first pair of ribs (figs. 1 and 3, tp.^, r.'). 
Each of the lateral surfaces of the complex centrum is traversed close to its 
anterior margin by a faint ridge (fig. 4, l.r.), which, commencing at the base of the 
accessory articular processes, passes obliquely backwards and upwards, and apparently 
indicates the anterior limit of the superficial bony deposit which invests both sides of 
the centrum. To the dorsal portion of this ridge, which may be called the “ lateral 
ridge” of the complex centrum, there is firmly attached, but except in old specimens not 
actually confluent with it, an elongated nodule of bone which terminates at its dorsal 
extremity in a thickened nodular prominence (figs. 3 and 4, r.n.). From the relations 
of this ossicle to the radial fibres of the malleus we shall in future refer to it as the 
“radial nodule.” The radial nodule generally coincides with the junction of the 
anterior third of the complex centrum with the posterior two-thirds, and according to 
Ramsay Weight, by whom, in Amiurus, it is apparently referred to as the “ oblique 
ridge,” indicates the line of union of the third and fourth vertebral centra in the 
formation of the complex centrum. In young specimens the nodule is united by 
fibrous tissue only to the lateral ridge but in older forms appears to become firmly 
anchylosed thereto. From the thickened dorsal extremity of the radial nodule, but 
separated therefrom in young specimens by a well-marked suture, a thin, narrow strip 
of bone (fig. 3, d.l.) extends obliquely backwards and outwards ventrad to the 
cardinal groove, which, in consequence, becomes at this point a complete canal, and 
ultimately passes on to the ventral surface of the posterior division of the transverse 
process of the fourth vertebra, and blends therewith by its anterior margin and 
pointed distal extremity, leaving, however, its posterior edge projecting in the form of 
a faint ridge. In mature or old specimens this process, which we shall call the “ dorsal 
lamina,” and the lateral ridge, form a continuous obliquely-disposed ridge of bone 
sti’etching from the side of the complex centrum to the transverse process of the fourth 
vertebra, the radial nodule then appearing as a small nodular projection from its surface. 
A thin but continuous superficial ossification more or less coiiipletely invests each 
side of the complex and fifth centra, and obscures all external indication of the 
intervertebral suture which separates them (figs. 1 and 3, s.os.). Each ossification is 
somewhat triangular in shape, with the broad base coincident with the ventro-lateral 
margins of the two centra, and its anterior and posterior margins converging 
towards the flattened root of the transverse process of the fourth vertebra, where the 
MDCccxcirr. — b. l 
