Rather more than two years ago ²³⁵ a paper was read before the Zoological Society of London, by Professors Bridge and Haddon, on the auditory ossicles of fishes; I was unfortunately unable to hear the paper read and as far as I know it has not yet been published, but before I left England Mr. Haddon was good enough to give me a verbal account of the chief results contained in it. One of these was that in many fishes, notably certain Siluroids, the processes of the air-bladder were produced outwards to the side-walls of the body, where the skin became very thin, forming a sort of tympanic membrane, the vibrations of which were transmitted through the air-bladder to the ossicula-auditûs and thence to the organ of hearing.

On dissecting the common Red Cod a short time since, I was interested to find a combination of the two arrangements just described. As no accessory auditory apparatus has, I believe, hitherto been described in any of the Gadidœ, I have thought it advisable to present the following account to the Institute.

On the hinder surface of a roughly-prepared skull of Lotella, there is on each side of the occipital condyle (fig. 1, o.c) a large foramen (au. f), bounded internally by the basi- and ex-occipitals (b.o, e.o), and externally by the opisthotic (op.o). If the skull is prepared with sufficient care, this foramen is seen to be filled with an extremely thin plate (l), formed partly of bone, partly of membrane: its inner half is strongly plaited and fan-like, and belongs to the basi-occipital: it is separated by a membranous interval from the outer half, which is formed by the opisthotic, and is nearly smooth. This lamina forms the lower part of the posterior wall of the auditory capsule: the foramen, with the lamina stretched across it, may be called the auditory fontanelle.

Immediately below and internal to this fontanelle is a large downwardly directed process (x) of the basi-occipital, serving for the attachment of some of the neck muscles, and having its hinder surface concave: immediately external to the fontanelle is a process of the opisthotic (y) also bearing a concave surface: and external to this again on the posterior surface of the parotic process is a third facet (z) furnished by the pterotic.

The walls of the air-bladder (fig. 2) are for the most part thick and tough, but on the anterior half of its dorsal surface they become so thin as to be hardly distinguishable from the periosteum of the vertebral column. Near its anterior end the bladder becomes markedly constricted, and in front of the neck thus formed dilates considerably, forming the cornua which pass outwards and slightly forwards and upwards with this anterior