1898.] OSTEOLOGY OF THE IMPENNES. 985 



Key to the Species. 



Aptenodttes. 



a. Size larger ; sternum 12 in. ; sternum and coracoid 15"7 in. A. forstcri. 



b. Size Bmaller ; sternum 9"5 in. ; sternum and coracoid 12 in. A. fatagonicui. 



Cataebhactes. 



a. Width across posterior lateral processes less than that across anterior lateral 



processes f C. chrysoeome. 



\ C. pachyrhynchtis. 



b. Width across posterior lateral processes greater than across anterior lateral 



processes C. chrysolophts. 



Sphektscus. 



a. Size larger ; sternum not exceeding 5"10 in. measured from between coracoid 

 grooves to free end of posterior lateral processes ; length of scapula less 

 than corpus sterni 8. Tnagellanicus. 



h. Size smaller ; sternum not exceeding 5 in. ; length of scapula equals that of 

 corpus sterni S. de/uersus. 



EUDTPTTJLA. 



a. Width across anterior and posterior lateral processes equal. E. minor. 



b. Width across anterior lateral processes greater than across posterior lateral 



processes E, albosignata. 



D. Peltic Girblb (p. 978). 



Key to the Genera. 



A. Length of ischium greater than width of pelvis across antitrochanter. 



a. Synsacrum very wide in front of acetabulum and greatly constricted in 



the region of the ilio-ischiadie foramen ; the ends of the sacral ribs 

 partially filling up the ilio-ischiadic foramen ; pre-ilium very long and 

 attenuated, more than twice width across pelvis at acetabulum ; ischium 

 longer than post-ilium ; pubis with the free ends directed slightly 

 downwards Aptenodytes, 



b. Synsacrum only slightly constricted in region of ilio-ischiadic foramen ; 



ends of sacral ribs not constricting size of the ilio-ischiadic foramen ; 



anterior end of pre-ilium with a strongly curved outer border. 



a'. Length of pre-ilium twice that of width of pelvis across antitrochanter ; 



distance from posterior border of the ilio-ischiadie foramen to the 



ilio-ischiadic notch at the posterior border of the innominate much 



greater than width of widest part of synsacrum Pygoscelis. 



b'. Length of pre-ihum less than twice width of pelvis across antitrochanter ; 

 distance from posterior border of ilio-ischiadic foramen to ilio-ischiadic 

 notch equal or nearly equal to width of widest part of synsacrum. 



a". Dorsal surface of synsacrum with the median ridge feebly developed 

 in the acetabular region Catarrhactes, 



b". Dorsal surface of synsacrum with a strong median ridge along its 

 whole length Spkeniscus. 



B. Length of ischium not exceeding vridth of pelvis across antitrochanter ; width 



across pre-ilium at widest part equals that across pelvis at antitrochanter. 



Eudypies. 



Pboc. Zool. Soc— 1898, No. LXV. 65 



