OF PIPA AMERICANA. 133 



comment is the absence of a separate foramen for its exit 

 from the cranium. 



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

 in regard to its origin or its course. Its roots form a 

 a very intricate chiasma. 



The olfactory nerve (ol.) arises from the anterior ex- 

 tremity of the olfactory lobe, passes out through the walls 

 of the skull, and distributes itself to the epithelium of the 

 nasal capsule and to the organ of Jacobson in two branches. 

 There is no indication of two roots like those described 

 by Wiedersheim in the Gymnophiona and which have la- 

 ter been commented upon by Burckhardt. 



LITERATURE. 



Von Plessin and Rabinowicz. Die Kopfnerven von Salamandra 

 maculata. Miinchen. 1891. 



A. Ecker. Anatomy of the frog. 1889. 



Jeffries Wyman. Anatomy of the Nervous System of Rana pipiens. 

 Smithsonian Contributions to Knowledge. Vol. V. 1852. 



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



R. Wiedersheim. Comparative Anatomy of Vertebrates. 1884. 



Rose. Uber die Entwickelung der Zahne des Menschen. Arch. f. 

 mik. Anat. xxxviii, 1881. 



T. H. Huxley. Amphibia, Encyclopaedia Britannica. 



EXPLANATION OF PLATE REFERENCE LETTERS. 



a.b.c. = terminal branches of nasalis. 



buc. =buccalis. 



com.gr. = 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. 



