No. 445-] OSTEOLOGY OF rvGOPODES. 



known to me. It is lamelliform, thin and narrow, its surface 

 being in the middle plane, while behind it is moderately bifur- 

 cated, to be carried to a sharp apex anteriorlv. l",itlKi niaxillo 

 palatine is a subconcavo-convex oval plate ot hone-, ot some 

 little size. Its mesial surface looks inwards and upwaids, 

 the anterior fourth bein^i^ fused almost indistin- uisliahK with 

 the nasal, maxillary, i)alatine and prcma.\illar\ . ralatmcs and 

 maxillo-palatines are well separated from each other in the mid- 

 dle line, and from the vomer. 



An OS quaratum is rather a large bone in the grebes, with a 

 long, gently-inturned orbital process. Its mastoidal head sup- 

 ports two facets of articulation, being sei)arated from each other 

 by a shallow sublongitudinal valley. Transx erselw the c|uadrate 

 is much compressed, and 1 have already described above the 

 process at its infero-internal angle to accommodate the hinder 

 end of the corresponding pterygoid. The mandibular portion is 

 much excavated centrally on its nether aspect, with a small 

 articular facette on either side of the concavity. There is also 

 an articular line bounding this dejiression posteriorly. The 

 bone appears to be pneumatic. 



Passing to the consideration of the mandible we find it to be 

 of the very acutely V-shaped pattern, with the ramal vacuity 

 completely closed in. The articular ends are enlarged and 

 abruptly truncated behind, where the\- show each a Hat triangu- 

 lar surface. The ramal sitles posteriorly are thin, lofty and flat, 

 to become narrower and thicker as they pass tai)ering forwards 

 to the acute ai^ex. The symphysis is short, slightly exc avated 



of the mandible that are at all p.neumatic. the usual pneumatic 

 orifice being at the end of the inturned, stumpy articular ternn- 

 nati<.n ..f the bone. Aside from the brevity of the sui)erior 

 osseous mandible in the short-billed grebes, the skull characters 

 as given above for Colyvibns hoUnrlli are substantially repeated 

 in them. \\\ l\>dilymbiis podu'ips,\M^\\iz\^\, I observe that the 

 anterior extremity of the vomer terminates in a small, rounded, 



ioned. It also has the mesial notch on the upper side of the 



