FELIS SPELtEA. 49 



bulla, always present in the skulls of Carnivora, and very largely developed in the genus 

 Felis, is a large chamber of oval shape, wedged in between the basi- and par-occipitals, the 

 mastoids, and the petrosal. Its external walls are very compact and hard, though thin, 

 and appear under the microscope to be somewhat fibrous in structure. It is closed on 

 all sides, excepting at the top, where there is a long fissure, in which the promontorium 

 of the petrosal lies in such a position that the "fenestra vestibularis" opens directly on 

 the interior of the bullar cavity. The latter passes into the chamber of the tympanic 

 proper. The bulla thus performs the same functions as the mastoid cells in man, and is 

 consequently called the mastoid by Straus-Durckheim and some other anatomists. In front 

 the bulla sends forward a long, solid, pointed process, that passes between, and articulates 

 with the posterior processes of the basi- and the ali-sphenoid. On the inside it is in contact 

 with the external and lower border of the basi-occipital, and with the whole length of the 

 petrosal. Its relations to the mastoid and paroccipital, to the foramen lacerum medium, 

 and the "stylo-mastoid" foramen, have been already described. In comparing these 

 bones with those of the large Eeles we labour under the disadvantage of being able to see 

 but a small portion of them in the perfect skulls. So far, however, as we have been able 

 to institute a comparison, the difference between the spelaean and leonine bones is so small 

 that it is scarcely worthy of note. There is absolutely no difference between the cere- 

 bellar surfaces of the petrosal. As compared with those of tigers, the inter-tympanic 

 width is greater in the Taunton skulls than in several skulls of tigers of similar size. 

 The foramen lacerum posterius is shorter and rounder in lions and Fells spelaa than in 

 the majority of tigers' skulls. These points, however, are of no great value, and are 

 certainly not characteristic. They show merely the leonine character of these bones of 

 Felis sjjelcea, which in the course of this Monograph wc shall be able to trace throughout 

 the rest of the skeleton. 



Malleus (PI. X, figs. 2, 3). — Wc found that in the tympanic of the larger skull at 

 Taunton the malleus still existed in its original position, and nearly perfect. We 

 extracted it, and are consequently able to give figures of it and describe it. The long 

 process (the "manubrium mallei"), which in the living animal rested on the drum of the 

 tympanic, sloped downwards and forwards, while the condyle-like head was articulated 

 very slightly to the upper part of the tympanic cavity, formed by the external edge of the 

 petrosal and the inferior and inner edge of the squamosal. The neck of the bone is bent 

 inwards and upwards, and posteriorly there is a small facet for the incal articulation ; on 

 the opposite side of the neck from that to which the manubrium is attached a small 

 sharp process rises, which afibrds insertion to the Eustachian muscle^ (''intern us mallei"). 

 In the living lion a thin plate of bone fills up the acute angle formed by the neck ; this 

 is broken in the fossil. Two other small processes rise from the opposite side of the 

 neck to the Eustachian process, which appear to be homologous with the process! longus 



^ Straus-Durckheim, op. cit., vol. i, p. 41G. 



