SlU'KEI.DT : OSTEOLOCY OF THF. PsiTTACI. 409 



On either side of these apertures are seen from three to four, or 

 sometimes only two, minute foramina. Well to the outer sides of 

 there are the conspicuous foramina ovalia. 



As has already been said in a former paragraph, the temporal wings 

 of the exoccipital are very prominently produced ; and, as usual to 

 their inner sides, at the basal angles of the l)asitemporal triangle are 

 found the ordinary group of foramina for the entrance and exit of ves- 

 sels and nerves. 



The foramen magnum is of a sulxircular outline, and the plane of 

 its periphery makes an angle of some 20° with the backwardly-produced 

 plane of the basis cranii. The condyle is comparatively large, hemi- 

 spherical in form, and sessile. In Ara the foramen magnum is in- 

 clined to be cordate in outline. 



Rising almost perpendicular to the basitemporal triangle, the occip- 

 ital area is well defined by an elliptical bounding arc, which sweeps 

 round on either hand to the apices of the temporal wings. In the mid- 

 dle of this space a moderately prominent, unpierced, supraoccipital ele- 

 vation is to be seen. In removing the cranial vault I find that the 

 tables are very closely juxta-opposed, and, in consequence, l)ut a lit- 

 tle diploic tissue present. The several cerebral fossae are sharply 

 defined by out-jutting lamelliform ledges of bone. 



At the base of the sella turcica there seems to be a common carotid 

 opening, and the posterior clinoid wall of this fossa is very thin, and 

 usually exhibits one or two perforations. 



The mandible (Plate I, Fig. i ) of Co minis is somewhat horseshoe- 

 shaped, with very deep and smooth ramal sides, which are deficient 

 anteriorly, leaving a semicircular opening with cutting edge all around. 

 When the horny mandibular sheath is carefully removed in the fresh 

 specimen, this edge has filiform prolongations of soft tissue standing 

 out from its middle third below, which after they have dried and be- 

 come more or less shrunken, look something like a row of delicate teeth. 



The ramal sides of this bone slope away as we proceed backwards, 

 and the mandibular ends are truncated at about the same angle. 



To the inner sides of these artic ular ends a ledge is thrown out to 

 support the facet for either (juadrate. Behind these longitudinal 

 articular grooves, single pits are found, at the base of which the pneu- 

 matic foramina occur. 



The under borders of the mandible are smooth and roundetl. The 

 nianilibles are very powerfully constructed in the Macaws and Cocka- 

 toos (See Figs. 3 and 4). 



