360 
DR. R. W. SHUEELDt’s MORPHOLOGICAL 
while a shallow, mid-longitudinal gutter traverses this part of the 
skull (fig. 19). 
Eegarding this part of the skeleton of the Purple Martin upon 
a lateral aspect (fig. 18), we are to note the form and compara- 
tively large size of the pars plana ( p.p .), the slender and rather 
small pterygoids, as well as the fact that the osseous interorbital 
septum is pierced by two large vacuities of a form in most speci- 
mens shown in the drawing. This figure displays so well the 
characteristics of the lateral part of the cranium proper in Progne, 
that any further account becomes superfluous. 
Turning to the base of this skull (fig. 20), we are to note the 
form of the vomer and the maxillo-palatines ; the first has very 
much the character of that bone as we usually find it in the Passeres. 
The maxillo-palatines have their median free extremities dilated, 
and they, as in all Swallows, are separated by several millimetres 
in the middle line. 
The palatines articulate with each other for the posterior two 
thirds of their length beneath the sphenoidal rostrum, and are in 
close contact at their pterygoidal heads, as in the pterygoids 
themselves in this latter locality. 
As in all Cypseline birds which I have examined, the posterior 
external angles of the palatines in Progne are somewhat drawn 
out, and then squarely truncated (compare figs. 19 and 22, pi).. 
Swallows have the occipital condyle very small, while the foramen 
magnum is relatively large, and its plane makes an angle with 
the basi-cranial plane of some eight or ten degrees. 
Posteriorly, the skull in Progne exhibits a large supra-occipital 
eminence, and an occipital area which is nearly circumscribed 
by a sharply defined occipital ridge or line, which defines its 
form as reniform, and placed transversely at this aspect of the 
cranium. 
Coming next to the mandible of this bird, we find it to be of a 
V-shaped outline, with its ramal sides shallow in the vertical 
direction, and with a symphysis of some depth anteriorly at its 
apex. There is a swell, on either side, at the superior ramal 
margins at points about where the horny theca ceases and the skin 
commences, when these latter parts are in situ. A small slit- 
like ramal vacuity exists, and the posterior angular processes are 
well-developeQ, though they curve up but very slightly. 
Essentially, the hyoidean apparatus is Passerine in character ; 
