356 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Yol. Yl. 



peripheries. The obclurator foramen is very small and varies in the fig- 

 ure of its outline, though generally assuming more or less the form of 

 the ellii3se 5 the broad and thin hinder blade of the ischium again dips 

 down to meet the slender pubic shaft, just before its termination, to shut 

 in an elongated spindle-shaped tendinal vacuity. (Fig. 100.) 



TJpon the ventral aspect of the pelvis, we note that the bone affords 

 no shelter whatever for the important organs it incloses until we pass 

 the fourth sacral segment and the very decided vertebral swelling to 

 form the sinus rhomboidalis ; it then drops into a deep depression on 

 either side, whose concavities and convexities correspond with those de- 

 scribed and attributed to the dorsal surfaces. The apophysial braces 

 thrown out by the vertebrae are extremely slender, except in the cases 

 of the first and fourth; the former segment bears a free pair of slender 

 l)leurapophyses, whose hsemapophyses articulate along the posterior 

 border of the ultimate sternal ribs, as do some of the inferior so-called 

 " costal cartilages" in anthropotomy, lacking the necessary length to ar- 

 rive at the costal borders of the great ventral hsemal spine, constituting 

 a common ornithic character. These sacral ribs rarely or never support 

 uncinate processes. 



Six segments are devoted, in this Shrike, to the coccygeal division of 

 the column, exclusive of the pygostyle ; they share the same fate, with 

 their fellows and representatives in nearly all of the class Aves, in hav- 

 ing many of their original vertebral components either rudimentary or 

 entirely suppressed ; the neural spines, hooking over each other, ante- 

 riorly, become more and more feebly developed as we proceed backwards ; 

 this order of things is just reversed when we come to examine the hypa- 

 l)ophyses on the nether aspects. The neural canal that passes through 

 them dwindles to mere capillary dimensions before reaching the " coc- 

 cygeal vomer", into which bone it barely dares to enter. 



The diapophyses of the caudal vertebrae are bent downwards, com- 

 pressed horizontally, broad, and show but slight differences in length, 

 before reaching the last one, in which they are shorter. The lamina of 

 the pygostyle has the outline of an isosceles triangle, being truncate at 

 its apex; the "body" below is of a substantial structure, barely dilated 

 behind, and otherwise presenting the usual characteristics as found 

 among the oscines. 



The bones of the scapular arch are all free and independent of each 

 other, the stability of their relative position depending upon strong lig- 

 aments in the living bird. The blade of the scapula is quite narrow, 

 and, in the vast majority of cases, extends across the dorsal pleura- 

 pophyses, its distal eud being obliquely truncate, from within, out- 

 wards ; the blade-like portion is brought uj) in close juxtaposition with 

 that portion of the bone that affords the scapular moiety of the glenoid 

 fossa. Its acromial process is very short, owing to the fact that it has 

 to proceed but a short way before it abuts against the much-expanded 

 head of clavicle, on either side ; it forms with the coracoid the usual ten- 



