AORTIC ARCHES OF BIRDS — GLENNY 



559 



type 1 thoracic artery; ligameiitum aortae present; presence of the 

 ligamentum botalli variable; vertebrals and superficial ccrvicals 

 usually arise separately from the common carotids. 



This order appears to be in a state of flux insofar as evolution of 

 the aortic arch system is concerned. This evolution is not restricted 

 to a single family, although the greatest evidence of carotid evolution 

 is to be observed in the Ardeidae. It has been found that, even within 

 the same species, both the bicarotid and conjugate carotid conditions 

 may occur, and that within a species which is normally conjugate 

 carotid, both the B-1 and the B-2 condition may exist. It may be 

 presumed, therefore, that further variation in the carotids may take 

 place, and that any apparent deviation in a condition as reported 

 may be accounted for on the basis of individual levels in the evolution 

 of this system. 



References: Finn, 1891; Garrod, 1873; Gleimy, 1940a, 1945c, 

 1953a. 



Family Ardeidae 



Carotids variable; presence of the ligamentum botalli variable. 



The high degree of variation in the dorsal carotids of this family 

 seems to indicate that these birds are undergoing further speciation, 

 at least with respect to the aortic arch system. 



Species studied 



By Finn 



Nycticorax violaceus — Nydanassa viola- 

 cea (Linne) (A-1) 



By GaiTod 



Ardea goliaih Cretzschmar (A-1) 



Ardea cinerea Linne (A-1) 



Ardea purpurea Linn6 (A-1) 



Ardea alba= Casmerodius albus albus 

 (Linn6) (A-1) 



Ardea egretta— Casmerodius albus egretta 

 (Gmelin) (A-1) 



Ardea garzetta— Egretta garzelta (Linn^) 

 (A-1) 



Ardea candidissima= Leucophoyx thula 

 (MoUna) (A-1) 



Nycticorax europaeus = Nycticorax nycti- 

 corax (Linn6) (A-1) 



Botaurus stellaris (Linn6) (B-1) 



By Glenny 



Ardea herodias treganzai Court (B-1) 

 Ardea herodias herodias Linne (A-1) 

 Butorides virescens virescens (Linne) (B-1) 

 Butorides sundevalli Reichenow (A-1) 

 Florida caerulea (Linne) (A-1) 

 Ardeola speciosa (Horsfield) (B-2-s) 

 Bubulcus ibis ibis (Linn6) (A-1) 

 Bubulcus ibis coromandus (Boddaert) 



(A-1) 

 Dichromanassa rufescens (Gmelin) (A-1) 

 Casmerodius albus albus (Linn6) (A-1) 

 Leucophoyx thula brewsteri (Thayer and 



Bangs) (B-1) 

 Hydranassa tricolor ruficollis (Gosse) 



(A-1) 

 Nyctanassa violacea pauper (Sclater and 



Salvin) (A-1) 

 Ixobrychus minutus minutus (Linne) 



(A-1) 

 Ixobrychus sinensis sinensis (Gmelin) 



(B-1) 

 Ixobrychus sinensis bryani (Seale) (A-1) 

 Botaurus lentiginosus (Montagu) (2) 



(B-1 and B-2-s) 



