CTUEE OF THE COLUMELLA AURIS IN THE PELYCOSAUEIA. 



95 



and then turns towards tb« base of the sluill. I trace it directly to a foraniou on the superior edge 

 of tlie sphenoid. It is clearly the facial portion of the seventh nerve (tensor tympani), as described 

 by Fischer and Stannins,* and has nothinj;- to do with the auricular bones and cartilages. The 

 only connection, then, with inferior arches which lean detect in this species is the fibrous one with 

 the mandible, and I am doubtful of the significance of this. 



It does not seem practicable to recognize the suprastapedial in the epicolumella of Clcpsydrops 

 hptocephalus.] It would require an excessive shortening of the columella, which might readily be 

 the condition of things in Clepsydrops. But it would require that the suprastapedial should be 

 ossified, and separated by suture from the remainder of the cartilage. Until some form is found 

 ill which this cartilage is segmented such a hypothesis has no foundation. The homology of the 

 epicolumella with the incus is, on the other hand, almost certain; first, by the evident propriety 

 of the exclusion of the stajjcs from the question, on account of its position, and by the history 

 of its origin as shown by Salensky; second, on account of its position relative to both the stapes 

 and the malleus. This being the case, the result follows that the doctrine of Peters that the quad- 

 rate bone is not the incus, as was maintained by Reichert, is the true one. J 



Efol 



Epol 



EXPLANATION OF PLATE. 



Fig. 1. Coh\me\laanT\so( Clepsydrojyslepiocejihulus; internal side. Fig. la, external side; 1ft, proximal extremity ; 

 Ic, distal extremity ; st., head of stapes; Etoh, epicolumella; d, distal articular surface, especially represented in Fig. , 

 Ic; c c, toramiua of stapedial can.al. All tigures aie half natural size, excepting Ic, which is natural size. — From the 

 proceedings of the American Philosophical Society, 1884, p. 46. 



Fig. 'i. Auricular bones and cartilages and adjacent parts of Selodeniia suspect urn Co\)e,§ twice natural size. Bo., 

 hasioccipital bone; J?i-o.,cxoccipital ; y., quadrate; J/n., mandible; P/., pterygoid ; J/. Pf., interual pterygoid muscle ; 

 VII, seventh nerve; Col., columella auris; HsI., hypostapedial process of auricular cartilage; Sst., suprastapedial 

 process; Est., epistapedial process; HI., hypostapedial ligament; El., epistapedial ligament. 



* Zootomie der Fische, p. 154. 



tSuch a hyjiothesis is suggested after inspection of Huxley's figure of these parts in Hatteria, in Anatomy of 

 Vertebrated Aninuils, p. 77, Fig. A. See also American Naturalist, 1884, p. 1253; Proceeds. Amer. Philosoph. Soc, 

 1884, p. 41. 



{See Proceedings Amer. Philosoph. Society, 1884, p. 41, where Peter's view Is maintained. 



§ I owe the specimen dissected to my friend Horatio N. Bust, who obtained it on the Gila River, Arizona. 



