ShU|-KI,I)T : OSTKOLOGV ()|- THE HeROI )IONKS. 21.3 



25. The hypo-tarsus of the tarso-nietatarsus 3-crestc{l, graduated in 

 size, the outer being the smaller ; the tendinal grooves pass between 

 them. In Xycfiiorax the two largest crests fuse across at their pos- 

 terior free margins, and convert the passage between them into a closed 

 canal for the tendon. 



26. Pes co.n[)3sed of well-proportioned phalanges, arranged on the 

 plan of 2, 3, 4 and 5 joints to 1-4 toes res])ectivelv. 



All of the forms of our North .\merican representatives of the genus 

 Ardea have the skull very much alike, except, of course, in the i)oint , 

 of size. In Ardea virescens and Nycticorax ?i. nrevius the skulls are 

 notably very much alike, no pronounced characters, in fact, distin- 

 guishing them ; while on the other hand Nycticorax violaceus has a 

 skull that is at once seen to be distinguished from the skull in Ardea 

 by its greater average breadth ; its comparatively much shorter beak : 

 by the form of its lacrymal bone ; by the difference in the amount of 

 interspace between the crotaphyte fossns ; and by the minute foramina 

 for the exit of the first jiair of cranial nerves as compared with the 

 large vacuities there in Ardea. Finally by the vertically truncate 

 posterior ends of the mandible, they being obliquely so in the latter 

 genus. 



The form of the lacrymal bone in these birds is an interesting one 

 for whatever other morphological differences may exist between the 

 representatives of the genera Ardea and Nycticorax, we can always 

 distinguish the skull of the former from any of the latter, so far as our 

 North American species go, by this bone alone. This difference per- 

 tains to the lower part of the lacrymal as set forth in my description 

 above (compare figures of skulls oi Ardea and Nycticorax given above), j 



While engaged upon the present memoir I have had before me skulls 

 of Cancroma cochlearia and other foreign heron-forms, for which my 

 thanks are due to the U. S. National Museum at Washington, 1). C. 

 Since that time some additional material has come to hand. Part of 

 this is my own and part belongs to the U. S. National Museum. I find 

 I have an imperfect skeleton of the Roseate S])Oonbill {Ajaja ajaja) ; 

 skeletons of the White Ibis {Guara allnx), White-faced Glossy Ibis 

 (^PUi^adis guarauna) ; and imperfect skeletons of a few other Ibises. 

 There are also two or three complete skeletons of Tantalus loculator 

 or the " Wood Ibis," together with a sternum and shoulder-girdle of 

 the Jabiru {^Mycteria americana). I have also complete skeletons of 

 the American Bittern {Botaurus lentiginosi/s) and Ardetta exilis. 



