OF PirA AMERICANA. 133 



comment is the absence of a separate foramen for its exit 

 froni the eranium. 



The optic nerve (op.) presents no special features, either 

 in reojard to its orio-in or its course. Its roots form a 

 a very intricate chiasma. 



The olftictory nerve (o?.) arises from the anterior ex- 

 tremity of the olfactory lobe, passes out throiigh the walls 

 ofthe skull, and distributes itself to the epithelium ofthe 

 nasal capsule and tothe organof Jacobson in two branches. 

 There is no indication of two roots like those described 

 by Wiedersheim in the Gyninophiona and vvhich have la- 

 ter been commented upon by Burckhardt. 



LITEEATURE. 



Von Plessin and Rabinowicz.— Die Kopf nerven von Salamanära 

 maculata. Münclien. 1891. 



A. Ecker.— Anatomy of tlie frog. 1889. 



Jeffries Wyman. — Anatomy of the Nervous System of Bana pipiens. 

 Smithsonian Contributions to Knowledge. Vol. V. 1852. 



J. G. Fischer. — Perennibranchiaten und Derotremen. 1864. 



R. Wiedersheim. — Comparative Anatomy of Vertebrates. 1884. 



Rose.— Über die Entwickelung der Zähne des Menschen. Arch. f. 

 mik. Anat. xxxviii, 1881. 



T. H. Huxley.— Amphibia, Encyclopsedia Britannica. 



EXPLANATION OE PLATE REFERENCE LETTERS. 



a.h.c. ■= terminal branches of nasalis. 



buc. =buccalis. 



com.g. = commissure of VII and IX. 



com. = commissure between palatinus and maxillaris. 



/. = frontalis. 



fac. = facialis. 



gph. glossopharyngeal. 



gas.gang. = ganglion of V and VII. 



hy.man. =hyomandibularis. 



man. = mandibularis. 



men. = mentalis. 



