zloS SxoDGRAss, Geospiza, Cotoniis, a>id Cer///idia. fo"!' 



the temporal crests. The surface is simply concave instead of 

 doubly convex. The temporal crests are relatively small and lie 

 far below the dorsal profile of the cranium, the space between 

 them being strongly arched instead of flat transversely. The 

 space between the postfrontal and squamosal processes is rela- 

 tively narrower than in G. strenua, but the former process ends in 

 advance of the other. The interorbital septum is thin, and is 

 perforated at its upper posterior angle by a hole which is a part 

 also of a foramen opening into the cranial cavity on each posterior 

 orbital wall. 



The angle of the tomium of the upper mandible with the zygo- 

 matic bar is 122°; i.e., the deflexure of the mandible is 58°. 

 This is 4° less than the deflexure in G. strenua. The angulation 

 of the culmen is about the same in the two species. The inter- 

 nasal septum is not complete in G.fortis, forming simply a deep 

 median keel on the under surface of the nasal bones. 



The lower mandible is slenderer than in G. strenua and the 

 coronoid process is not so high- 



Geospiza fulighiosa parvula (Gould). (Plate XVII, Figs. 6 aiid 

 7.) — The structure of the skull in this species is very similar to 

 that of G. fortis, but in it the points in which the G. fortis skull 

 departs from the G. strenua skull are still more intensified- Both 

 the temporal and lambdoidal crests are comparatively slight. The 

 temporal crests are situated far down on the sides of the skull, 

 and the top of the skull between them is high and roundly convex. 

 The interorbital space is narrow and simply concave. 



The angulation of the culmen is considerably less than in the 

 other two species described. The deflexure of the upper mandi- 

 ble from the horizontal of the zygoma is 50°. This is 8° less than 

 in G.fortis. The nasal septum is entirely lacking. 



This is one of the smaller-billed species of Geospiza and the 

 skull differs conspicuously from that of G. strenua in the much 

 slenderer upper mandible and in the general lighter appearance 

 of the preorbital parts. The basal depth of the upper mandible 

 is contained 2^ times in the greatest depth of the cranium. 



Geospiza fuliginosa acutirostris (Ridgway). (PI. XVII, Figs. 8 

 and 9.) — The skull of this form differs from that of G.f. parvula 

 in the slightly slenderer, more tapering and less deflexed upper 



