4 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



vertebrates, an osseous connection, distinct from that formed by the stapes with the foramen ovale 

 of the os petrosum. From this it follows that the stapes cannot be regarded as the proximal 

 extremity of the visceral arch of which the columella forms a part, as its appearance in other rep- 

 tiles would lead us to infer. It also lends support to the view of Salensky, which is accepted by 

 Fraser, that the stapes is not an ossification of the cartilage of the visceral arch, but is an ossifi- 

 cation of the tissue surrounding the mandibular artery. 



Second. That the stapes resembles that of the Mammalia, and differs from that of other rep- 

 tiles in the perforation below its head. 



Third. That it is succeeded distally by a cartilaginous element, as in many other reptiles, which 

 is the triangular ligament of Cuvier, and is functionally the analogue, and probably the homologue 

 of the malleus of the Mammalia. 



The homology of the proximal extremity of this columella may now be considered. It cannot 

 be the suprastapedial cartilage of Huxley, since that is a superior process of the distal cartilagi- 

 nous element or malleus. It appears to be unrepresented in the reptilian columella, and I have 

 therefore called it the epicolumella* (Figs. 1, Ecol). 



In order to obtain some light on the homologies of the parts of this element, I have compared 

 it with the corresponding parts in various species of reptiles and batrachians', several of which 

 have been figured by Messrs. Huxley, Peters, and Parker. I have examined the ear bones and 

 cartilages of the Heloderma suspectum, and append herewith the result of my observations: 



The columella has the length usual in the Lacertilia, ceasing a short distance proximad to the 

 eustachian foramen. The cartilage, which continues in the same straight line, is divided at the 

 eustachian foramen, one process passing downwards on its anterior border, the other forming its 

 superior border. The posterior branch continues downwards for a short distance and terminates 

 in a point, which is connected by a short ligament with the extremity of the pterygoid bone (Fig. 

 2 hi). Immediately exterior to it, a slender, rod-like ligament descends in close contact with it. It 

 extends farther, however, reaching the articular bone of the lower jaw immediately posterior to 

 the cotylus for the quadrate (Fig. 2 el). Its subsequent course will be mentioned below. It appears 

 to be the ligament which Peters has represented as continuous with the descending process of 

 the stapedial cartilage, and on which he based his belief in the continuity of the latter with the 

 cartilage of Meckel. Its superior connection is, however, not with any part of the ossicula 

 auditus, but it can be traced to a point above the external extremity of the exoccipital bone. 



The stapedial cartilage extends beyoud the superior edge of the large eustachian foramen to 

 the membranum tympani, and is there decurved, extending in contact with it for 2-3 mm. and 

 terminating in an acute apex. Near the point where it reaches the membrane it sends a branch 

 upwards and backwards (Fig. 2 sst.) the suprastapedial cartilage, which forms a slender rod. The 

 suprastapedial reaches inwards, and terminates at a point on the inferior side of the exoccipital 

 bone at a point a little within opposite the origin of the inferior branch. It is only connected 

 with the horizontal cartilage below it by membrane, and it does not form a fan-shaped plate as 

 represented by Peters in Stellio and Huxley in Hatteria. 



The following are the connections of the cartilages with adjacent elements : The distal extremity 

 is acuminate and lies for a short distance on the membrauuni tympani, where it terminates without 

 continuation. From the convexity of the curve formed by the inferior edge of the cartilage where 

 it turns upwards, backwards, and inwards to form the suprastapedial, a narrow and weak baud 

 descends. It passes along the posterior border of the eustachian foramen, and terminates on the 

 superior edge of the mandible. As it descends it thins out and becomes indistinguishable as a 

 distinct rod or baud. The slender rod already described as descending to the mandible from the 

 descending process of the cartilage along the inner border of the eustachian foramen is figured by 

 Peters in Uromastix spinipesA He describes "it as a fibrous thread, which was formerly cartilag- 

 inous and connected the malleus with Meckel's cartilage." According to the figure it is not con- 

 tinuous with the inferior process of the cartilage ("malleus"). In Heloderma suspectum it passes 

 anterior to the cartilage, in close contact with it, to a point superior to the suprastapedial process, 



* American Naturalist, 1884, p. 1254. 



t Monatsbericute Akademie Berlin, 1«74, 44 f. B. 



