CoLYMBIDiE.] 



03TEOLOGIA AVIUM. 



[CoLYMBINiE. 



Colymbus, Linn. 



Glacialis, Linn. 



I have only the sternum and pelvis of this bird. 



Sternum large ; keel slightly arched on its lower edge, point projecting slightly 

 beyond the anterior edge of the sternum; hinder margin with two large fissures ; 

 xiphisternal portion very large, and projecting far backwards ; hinder margin wider 

 than the anterior margin. 



Furculum very broad at its junction with the coracoids, and gradually narrowed to its 

 junction with the point of the keel. 



Coracoids short, very strong. 



Pelvis narrow ; ilium and ischium much bent downwards, and with a long spine 

 proceeding from the former on each side of the ischiadic and caudal vertebrae ; os pubis 

 very broad at its extremity ; obturator foramina very large. 



Colymbus, Linn. 



Septentrionalis, Linn. 



Cranium. Palatine bones broadest a little anterior to the interarticulars, both turned 

 downwards, gradually sloping off forwards ; interorbital septum with two foramina ; 

 impressions of the masseter muscles very strong. Inferior maxillary bones slightly 

 prolonged beyond the condyles, cup shaped, a deep groove on each side over the 

 orbits. 



Sternum, pelvis, and furculum as in Colymbus glacialis. 



JRibs with very long styliform processes. 



Wing-bones. Humerus much longer than the ulna. 



Leg-bones. Tibia very much prolonged at its proximal extremity ; femur very short, 

 calcineal bones projecting far backwards at the upper part of the metatarsi, a foramen 

 through them for the passage of the contractor muscles, and a channel both down the 

 front and back of the metatarsus. 



Measurements. 



Tenths. 



Length of humerus ..... 54 



Length of ulna 44 



Length of metacarpus .... 23 



Length of femur 13 



Length of tibia 60 



Length of metatarsus . . . . . 27 



Length of sternum 55 



Tenths. 



Breadth of posterior margin of sternum 23 J 

 Breadth of anterior margin of sternum 21 

 Depth of keel ....... 5J 



Length of head ....... 43 



Breadth of head 11 



Length of pelvis . . . . . . 53 



Breadth of pelvis ■ . . . . . . 16 



o 213 



