360 



DR. R. W. SHUFELDt's MORPHOLOGICAL 



wliile a shallow, mid-longitudinal gutter traverses this part of the 

 skull (fig. 19). 



Eegardiug this part of tb.e 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 phma {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 tlie 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 exa?niued, 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 mandihle of this bird, we find it to be of a 

 Y-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-developea, though they curve up but very slightly. 



Essentially, the hyoidean apparatus is Passerine in character ; 



