1905. J OSTEOLOGY OP THE EURYL^EMTD.^. 33 



Passeres. In shape and position, however, this group of foramina 

 more nearly resembles its counterpart in the Bucconidse. These 

 foramina form a sort of cribriform plate guarding the mouth of 

 the recessus ti/mpanicics posterior, which is much reduced. The 

 recessus tympanicios sicp>erior is of small size, and opens externally 

 into the tympanic cavity by a small aperture lying between the 

 squamosal and otic heads of the quadrate. The aperture is 

 bounded externally by a short, pointed processics articularis 

 squamosi. 



The Squamosal Prominence. — It has already been pointed out 

 (p. 32) that the constriction of the temporal region of the 

 cranium has given the tympanic region a sort of individuality not 

 met with in the skulls of the higher Passeres, but common among 

 the lower types, and among the Ooraciiformes. 



In the Eurylsemid^e the free edge of this prominence projects 

 shelfdike beyond the head of the quadrate. It is continued 

 forwards into a hastate 2^'>'ocessus zygomaticus squamosi directed 

 downwards and outwards. From the base of the inferior surface 

 of this process projects a short pointed processus arfAcularis 

 squamosi ; between these two processes the head of the quadrate 

 is firmly grasped. 



The temporal fossce are especially deep in Cory don. As in other 

 genera, they are linguiform in shape and do not extend inwards 

 beyond the outer border of the supraoccipital fossa. 



The trigeminal foramen pierces the skull- wall at about the level 

 of the otic articular process for the squamosal, but some con- 

 siderable distance mesiad thereof. 



The orhito-sphenoid does not ossify. The interorhital septum is 

 largely fenestrated. 



The interorbital region of the frontals is generally very narrow 

 so that the orbits are only very partially roofed. In front the 

 orbit is bounded by a H-shaped antorbital plate. In Galyptomena 

 the interorbital region is wide. 



. The lachrymal, in Calyptomena (PL II. fig. 2, Z.), has the form 

 of a sigmoid rod more or less clubbed at each end. The upper end 

 woidd perhaps more correctly be described as hammer- shaped, and 

 is completely overshadowed by wide expansions of the frontal. 

 The whole ossicle is embedded in a groove carved out of a very 

 much swollen antorbital plate. The close resemblance between 

 the lachrymal of Galyptomena and that of Chasmorhynchus is 

 most remarkable. Both are embedded in the antorbital plate, and 

 both have the same sigmoid flexure. Only in the larger size of the 

 orbital end can the lachiymal of Chasmorhynchus be distinguished 

 from that of the Euryleemid Calypto'inena. 



In all the other Eurylfemidse, however, the lachrymal appears 

 to have been lost ; further, the antorbital plate has been reduced 

 to a thin t—- shaped plate. 



The Ethmoidal Region. — The mesethmoid is greatly reduced by 

 the fenestration of the interorbital septum. The antorbital plate 

 which bounds the orbit in front is j— -shaped and attached to 



Proc, Zool. Soc— 1905, Yol. II. No. III. 3 



