ifferences 565

SUMMARY 567

LITERATURE CITED 573

INTRODUCTION

Most descriptions of the circulatory system of birds, largely the work
of Glenny, have dealt with arteries of the neck and thorax in a wide
variety of species. As a result of his work, Glenny offered several
hypotheses concerning the phylogenetic, hence taxonomic, significance of
differences in some of these vessels. He also described six types of
thoracic arterial arrangements and stated that these categories might
represent various levels of evolution (Glenny, 1955:543-544).

The families Columbidae (pigeons) and Hirundinidae (swallows) have two
nearly extreme arterial types described by Glenny, and are universally
acknowledged as monophyletic. Differences within the families,
therefore, can be considered as valid intrafamilial differences. I have
investigated the thoracic and coracoid arteries and their branches in
members of these two families to determine the degree of individual
variability of the vessels, and the possible causes of interspecific and
intrafamilial differences.

METHODS AND MATERIALS

All specimens studied are in The University of Kansas Museum of Natural
History. They were preserved in alcohol and their blood vessels were not
injected. Dissections were made with the aid of a binocular microscope
at magnifications of 10x and 20x.

Following is a list of the species studied, the number of individuals of
each species dissected, and the catalogue numbers of the specimens. The
nomenclature and classification are those of the American
Ornithologists' Union's _Check-List of North American Birds_, fifth
edition (1957).

Family Columbidae

_Zenaidura macroura_ (Linnaeus), Mourning Dove 2: 40325, 40326.
_Zenaida asiatica_ (Linnaeus), White-winged Dove 1: 40328.
_Scardafella inca_ (Lesson), Inca Dove 5: 34894, 34896, 34902, 34906,
34907.
_Columba livia_ Gmelin, Rock Dove (domestic pigeon) 1: 40321.

Family Hirundinidae

_Iridoprocne bicolor_ (Vieillot), Tree Swallow 1: 38101.
_Progne subis_ (Linnaeus), Purple Martin 5: 37711, 38794, 38796,
38798, 38804.
_Stelgidopteryx ruficollis_ (Vieillot), Rough-winged Swallow 1: 38277.
_Riparia riparia_ (Linnaeus), Bank Swallow 2: 38784, 38785.
_Hirundo rustica_ (Linnaeus), Barn Swallow 1: 38839.

The following descriptions are