PLATE I a. 



Recent Sirenoidei. 



Fig. 



1. Skull of Protopterus annectens, Ow. 



Na. Nasal. 



Pt. pal. Pterygo-palatal. 



Qu. Quadrate. 



E. 0. Ex-occipital. 



Op. Opercular. 



/. op. Inter-opercular. 



D. Dentary. 



Ang. Angular. 



Hy. Hyoid. 



2. Skull of Ceratodus Forsteri, KrefTt. 



PL 0. Post-orbital. 

 Sq. Squamosal. 



3. Skull of the same. The lateral cartilages are largely removed, and the right 



ramus of the mandible is turned. 

 Fr. Frontal. 



4. Pterygo-palatal of C. Forsteri, to show the process for union with the frontal. 



Figs. 1 — 3 are mainly from specimens in the Museum of the College of Surgeons. All 

 the figures are of the natural size. The blue tint indicates cartilage. 



