180 ME. W. K. PARKER ON THE STRUCTURE AND 



Fig. 6. Os hyoides of Sfruthio, " C. ;" 2 diameters. 



Fig. 7. Vertical section of anterior part of skull of Struthio, " C. ;" 2 diameters. The 

 oblique lines 1-1 to 6-6 show where the sections in Plate X. were taken, 

 viz. 1, 1 to fig. 1, 2, 2 to fig. 2, &c. on to 6, 6, which answers to fig. 6. 



Fig. 8. End view of skull of Struthio, " C. ;" 2 diameters. 



Fig. 9. Part of primordial skull of (S'^rM^/wo, " C. ;" 2 diameters: eu. Eustachian groove ; 

 a.r.q. articular facet on the exoccipital wing for os quadratum ; f.s.r. fenestra 

 rotunda vel cochleae. 



Fig. 10. Vertical section of the skull of Struthio, " C. ;" 2 diameters : 5. foramen 

 ovale, with f. rotundum in front of it ; m.k. Meckel's cartilage ; sp. splenial ; 

 cr. coronoid. 



Fig. 11, Section taken transversely through pars plana, and end of inferior turbinal of 

 Struthio, "C. ;" 4 diameters: m.t.b. middle turbinal fold; i.t.b. base of infe- 

 rior turbinal ; ext. external aspect of pars plana ; int. internal ditto. 



PLATE IX. 



Fig. 1. Shea americana, var. Primordial skull, seen from above : p.f. postfrontal ; 



2 diameters. 

 Fig. 2. Side view; 2 diameters. 



Fig. 3. Entire skull, side view: d.n.g. duct of nasal gland; 2 diameters. 

 Fig. 4. Entire skull, lower view ; 2 diameters. 

 Fig. 5. Entire skull, upper view ; 2 diameters. 

 Fig. 6. Entire skull, end view ; 2 diameters. 

 Fig. 7. Os hyoides ; 2 diameters. 



PLATE X. 



Fig. 1. Transversely vertical section of skull of Struthio, "C." in front of the eye-ball, 



seen from behind ; 4 diameters: a.i.t. angle of inferior turbinal. 

 Fig. 2. A similar section further forwards; 4 diameters: n.px. nasal process of pre- 



maxillary ; i.t. inferior turbinal ; s.n. septum nasi. 

 Fig. 3. Another section a line or two in advance of the last ; 4 diameters : n.t. nasal 



turbinal. 

 Fig. 4. Another section in front of the last ; 4 diameters : a.px. angle of premaxillary. 

 Fig, 5. Another through the alae nasi; 4 diameters. 

 Fig. 6. Another in front of the alse nasi ; 4 diameters. 

 Fig. 7. Vertical longitudinal section of primordial skull of Wiea ; 2 diameters : i.o.s. 



interorbital space ; 5 a. foramen rotundum. 

 Fig. 8. Hhea Americana, var. Part of skull, side view ; 4 diameters. The outer part 



is pared away to show the semicircular canals. 



