1905. ] OSTEOLOGY OF THE EURYLEMIDA, 33 
Passeres. In shape and position, however, this group of foramina 
more nearly resembles its counterpart in ‘the Bucconidee. These 
foramina form a sort of cribriform plate guarding the mouth of 
the recessus ty ympanicus posterior, which is much reduced. The 
recessus tympanicus superior 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 processus 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 Coraciiformes, 
In the Huryleemidz the free edge of this prominence projects 
shelf-like beyond the head of the quadrate. It is continued 
forwards into a hastate processus zygomaticus squamosi directed 
downwards and outwards. From the base of the inferior surface 
of this process projects a short. pointed processus articularis 
squamosi; between these two processes the head of the quadrate 
is firmly grasped. 
The temporal fosse are especially deep in Corydon. 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 orbito-sphenoid does not ossify. The inéerorbital septum 1s 
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 f--shaped antorbital plate. In Calyptomena 
the interorbital region is wide. 
The lachrymal, in Calyptomena (Pl. II. fig. 2, U.), has the form 
of a sigmoid rod more or less clubbed at each endl The upper end 
would 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 Calyptomena 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 lachrymal of Chasmorhynchus be distinguished 
from that of the HKurylemid Calypiomena. 
In all the other Eurylemide, however, the lachrymal appears 
to have been lost; further, the antorbital plate has been reduced 
to a thin e-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 -shaped and attached to 
Proc, Zoot, Soc,—1905, Vou, Il. No. ILI. 3 
