IN THE PAEAaUAYAJs LBPIDOSIKEN, ETC. 375 



42. "WiEDERSHEiM, R. — Salmnandriiia perspic'dluta wnA Geotriton fuscus. 1875. 



43. Idem. — Das Kopfskelet dcr Urodelen. Leipzig, 1877. 



44. Wilder, H. H. — Die Nasengegend von Menopoma alleghaniense und Amphiuina tridactijliint, 



Zool. Jahrbiicher, Bd. v. Heft 2, 1892. 



45. Woodward, A. S. — British Museum Catalogue of Fossil Fislies, pt. ii. 1891. 



VI. EXPLANATION OF THE PLATES. 



The cartilaginous portions of the skull are tinted blue. Unless otherwise stated, the 

 figures are of the natural size. The lettering is uniform in both Plates. 



PLATE XXVIII. 

 Fig. 1. Lateral view of the skull of the Paraguayan Lepidosiren. 

 Fig. 2. View of dorsal surface. 

 Fig. 3. Ventral view. The cerato-hyal, cranial rib, and Interoperculum of the left side 



have been removed. The vestigial hyoidean ray of the right interoperculum 



is not shown. 

 Fig. 4. Vertical longitudinal section of the skull. 

 Fig. 5. Dorsal view of the nasal region and the anterior portions of the palato- 



pterygoid and fronto-parietal bones. The ectethmoids have been removed. 

 Fig. 6. View of the periotic capsule from the interior of the cranial cavity. X 2. 

 Fig. 7. External lateral view of the lower jaw. 

 Fig. 8. Internal lateral view. 



PLATE XXIX. 



Fig. 9. External view of the mandibular symphysis. 



Fig. 10. Branchial arches of the left side. 



Figs. 11-19. Tranverse sections through the skull at the various points indicated by 



C-D 

 E-F 



„ G-H ,, 



K-L „ 



M-N „ 

 O-P 

 Q-R 



Fig. 20. Transverse section through the nasal region of Ceratodus fosteri. 

 Fig. 21. Outline lateral view of the skull of the Paraguayan Lepidosiren to show the 

 planes in which the transverse sections (figs. 11-19) have been taken. The 

 ectethmoids, opercular bones, and the hyoid arch have been removed. 



