SHOULDER-GIRDLE OF ICHTHYORNIS. 145 



The coracoid of Apatomis resembles in general that of Iclitliyornis, hut 

 is less expanded at the lower or sternal end ; and these ends overlapped 

 much less extensively than in that genus, if indeed they overlapped at all. 

 The articular surface for the scapula is, as in Iclitliyornis, a hemispherical 

 cup, but it is placed almost wholly below the articular surface for the 

 humerus, or the coracoid part of the glenoid cavity. 



The articulation for the humerus is comparatively broader than in 

 Ichihyornis, and is excavated in the middle, instead of being nearly flat, 

 as in that genus. Under and beyond these articular faces, the coracoid 

 is flattened vertically, almost to an edge, below. The shaft of the bone 

 is bent strongly inward beyond the glenoid cavity, instead of continuing 

 nearly straight, and there is a pronounced terminal knob, but no distinct 

 face for articulation with the clavicle. The glenoidal, or subscapular, pro- 

 cess is perforated by a foramen at its base, as in Iclitliyornis. The shaft 

 of the coracoid is hollow. 



Measurements of the coracoids in the types and some other specimens 

 of Iclitliyornis and Apatomis are given below. 



Measurements of Coracoid. (Ichthyomis dispar, No. 1450.) 



Length of sternal articulation, 16. mm 



Greatest antero-posterior diameter of proximal end, 1.7 



Antero-posterior diameter of shaft, where broken, 2.2 



Transverse diameter of shaft, where broken, 4. 



Measurements of Coracoid. (Ichthyomis dispar, No. 1718.) 



Length of humeral articulation, . 6. mm 



Greatest transverse diameter of humeral articulation, 3.4 



Transverse diameter of shaft, below humeral articulation, 3.8 



Vertical diameter of clavicular process, 5. 



Transverse diameter of clavicular process, 2.2 



Measurements of Coracoid. (Ichthyomis victor, No. 1452.) 



Length of humeral articulation, - 6.5 mm 



Greatest transverse diameter of humeral articulation, 4. 



Least transverse diameter of shaft, below articulation, 3.5 



Vertical diameter of clavicular process, 5.2 



Transverse diameter of clavicular process,. 2.8 



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