MUSEUM OF COMPARATIVE ZOOLOGY. 



29 



much as in the males of the eared are not partially united as in Phoca, 

 seals. but merely touch each other at their 



extremities, and arc most widely sep- 

 arated at the middle. 

 The ischia are dorsally arched, es- The ischia are considerably arched 

 pecially their dorsal margins, which above, but otherwise have nearly the 

 rise in a high angular point opposite same form and size as the pubic 

 the posterior third of the thyroid bones. Their dorsal margins have 

 foramen. Anteriorly they are sub- not the high angular prominence 

 cylindrical, but posteriorly are flat- seen in Phoca. 

 tened into broad thin blades, and 

 unite with the corresponding parts of 

 the pubic bones. 



The thyroid foramen is an irregular The form of the thyroid foramen is 

 elongated ellipse, its pubic outline be- nearly the same as in Phoca. 

 ing nearly straight. 



The ilio-pubic spine is prominent, The ilio-pubic spine is very large, 

 but the iliac tuberosity is wholly ab- and the iliac tuberosity is not only 

 sent. present, but is enormously developed. 



The middle of the acetabulum is The middle of the acetabulum is 

 situated a little in front of the pos- situated but a little in front of the 

 terior end of thejirst sacral vertebra, posterior end of the second sacral 

 which is considerably anterior to its vertebra, — the length of the second 

 position in the eared seals. sacral vertebra posterior to its posi- 



tion in Phoca. 

 Four fifths of the length of the Only slightly more than one half 

 innominate bone is posterior to the of the length of the innominate bone 

 acetabulum, — in other words, the is behind the acetabulum. Hence 

 proportion of the length of the ischio- the proportional length of the ischio- 

 pubic part to the length of the ilia pubic portion to the ilium is nearly as 

 is as three to one. one to one. 



The bones of the pelvis are all thin The bones of the pelvis are all 

 and slender. thick and stout, especially the walls 



of the acetabula. The acetabula are 

 themselves very much larger than in 

 Phoca. 



In recapitulation it may be stated that the essential or most striking 

 pelvic differences in the males between Phoca and Eumetopias and Cal- 

 lorhinus consist in the abbreviated ilia, with their outwardly produced 

 crests, the greater elongation of the pubic and ischiac bones, and the more 

 anterior situation of the acetabula in Phoca as compared with the others. 



