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Show 1869.] THE MALLEUS AND THE INCUS OF THE MAMMALIA. 393 Cuvier (Ossemens Fossiles, ix. p. 177) states of the stapes of the Crocodile, that " it consists of a long narrow elliptical plate, attached to the fenestra ovalis, from which passes a long and slender stem, which goes, becoming a little softer, to attach itself to the tympanic membrane ; it then bends back and follows it, being fixedly attached thereto and taking a cartilaginous consistency, as far as its posterior margin. From the posterior wall of the tympanum a muscular filament proceeds and becomes attached to the stem of the bone at about a third of its length [from the tympanic membrane] ; and a fold of the internal lining of the tympanum forms a triangular ligament which extends to the same point, and thus contributes to fix the stem to its recurved and tympanic portion." Windischmann observes, "Ossiculum auditorium Scarpa delineavit, fere quatuor lineas longum, operculo triangulari instructum. In altera extremitate in cartilaginem tripartitam desinit, cujus una pars, ut dixi, in membrana media tympani adhaeret, aliae duae in falce membranam hancce excipiunt." (Windischmann, De penitiori auris in Amphibiis structura. 1831.) The "triangular ligament" of Cuvier is clearly the "malleus" of Prof. Peters ; and the same part seems to be meant by the " alise duse " of Windischmann. What Cuvier terms the " stem " of the stapes of the Crocodile is more or less completely ossified ; but I find, in all cases, that it passes directly into the cartilaginous axehead-like plate, the convex edge of which is connected with the membrana tympani. There is no trace of the joint described by Prof. Peters in any of the specimens I have examined; neither have I been able to see anything of the "filiform tendon" which is said to "proceed from the posterior boundary of the tympanic cavity." Where the outer end of the stem of the stapes widens out into this process for the tympanic membrane, which I shall call the " extrastapedial" cartilage (fig. 1, E.St), it gives off, upwards and backwards, a slender cartilaginous prolongation, which expands and becomes the second "axehead-like" process, called " malleus" by Prof. Peters (S.St); but I have not been able to detect any trace of what Prof. Peters calls " a little short cylindrical intermediate cartilage " between this and the stem of the stapes. In all the specimens I have examined there is complete cartilaginous continuity between the two. What Prof. Peters terms the " cartilaginous margin of the tympanum " is a backward prolongation of the cartilage of the periotic region of the skull, which corresponds in part, if not wholly, with the tegmen tympani of a mammal. It may be called the " parotic process" (fig. 1, Pc.c) ; and in the adult it is converted, in great measure, into a slender and curiously curved process of the pro-otic, and, in part, into a process of the so-called exoccipital bone. Muscular fibres, which represent the stapedius muscle (fig. 2, Stp), proceed from this cartilaginous margin, or the corresponding bones, to the margin and outer face of the cartilage called "malleus" by Prof. Peters, but which I shall term the " suprastapedial" carti- |