408 ANNALS NEW YORE ACADEMY OF SCIENCES 



SECTION OF BIOLOGY 



8 Makch, 1915 



Section met at 8:15 p. m.^ Yice-President Eaymond C. Osbum pre- 

 siding. 



The following j^rogramme was then offered: 



L. A. Adams, Phylogexy of the Muscles of Masticatiox ix Yerte- 



BRATES. 



SuM^iARY OF Paper 



Mr. Adams said in abstract : The object of the investigation, which 

 had been carried on at the American Mnsenm of Natural History, was 

 to discover the evolutionary history of the jaw muscles in vertebrates and 

 to establish the homologies of the different elements throughout the verte- 

 brate classes. While many anatomists had made intensive studies of the 

 innervation of the muscles, very few had attempted to follow the muscles 

 through the vertebrate classes, and no one had given an adequate series 

 of figures. A series of 26 existing types of vertebrates had been carefully 

 studied and figured, representing the Elasmobranchii, Chondrostei, Ho- 

 lostei, Teleostei, Crossopterygii, Dipnoi, Ilrodela, Anura, Chelonia, Ehyn- 

 chocephalia, Lacertilia, Crocodilia, Aves and j\Iaimnalia. From the data 

 thus obtained and by applying the principles that became apparent as the 

 work proceeded, reconstructions of the jaw musculature were attempted 

 in a series of extinct forms representing the Arthrodira, the Temno- 

 spondyli, the Cotylosauria, the Cynodontia and the Theropoda. The 

 muscles under consideration fall under two main groups : first those inner- 

 vated by the ramus mandibularis of the trigeminus nerve (here belong 

 the temporalis, the masseter and the pterygoid muscles, as well as the 

 tensor tympani), and secondly those innervated by the facialis nerve, 

 including the posterior belly of the digastric, and in lower forms certain 

 muscles of the hyoid and opercular regions. The first group is derived 

 ultimately from the "adductor mass" in Elasmobranchs, the second from 

 the hyoidean adductors (constrictor dorsalis 2), as held by Yetter and 

 others. 



The speaker illustrated the history of each of these groups in the dif- 

 ferent classes of vertebrates.^ 



Dr. W. K. Gregory, in discussing Mr. Adams's paper, spoke of the 

 bearing of these studies upon the morphology of the skull, especially in 



^ Mr. Adams' memoir on this subject has since been accepted for publication by the 

 Academy. 



