198 TEETIAET VERTEBEATA OE THE EATtTM. 



that Dr. Elliot Smith is of opinion that their generic separation would be justified by 

 this diflFerence alone; (3) the os innominatum is much less reduced and has a com- 

 pletely closed obturator foramen and a well-defined acetabulum with which a functional 

 femur probably articulated, whereas in JEosiren the reduction of the pelvis has proceeded 

 almost as far as in Halitherium. These particulars are taken partly from Abel's paper 

 above referred to, and partly from a skull and mandible of Eotherium recently acquired 

 by the Geological Museum, Cairo : to this specimen further reference, with figures, is 

 made below, 



Frorastomus *, another primitive Sirenian from the Lower Tertiary beds of Jamaica, 

 differs from the present form both in the general shape of the skull, the slight deflection 

 of the snout, the absence of enlarged anterior incisors, and in the form of the 

 mandibular symphysis. 



Halitherium {Profotherium)veronense,Zignof, approaches this genus very nearly, but 

 in it the dentition seems to have already undergone considerable reduction. 



Eosiren libyca, Andrews. 

 [Plate XX. figs. 1-7; text-figs. 64, 65, 68 B.] 



1902. Eosiren lilyca, C. W. Andrews, Geol. Mag. [4] vol. ix. pp. 293-4, figs. 1-3. 

 1904. „ „ 0. Abel, Abhandl. k.-k. geol. Reichsanst. vol. xix. pt. 2, passim. 



Type Specimen. — A nearly complete skull described and figured, loc. cit. ; Geological 

 Museum, Cairo. 



This is the type and only species of the genus at present known. 



Form. & Log. — Qasr-el-Sagha beds (Middle Eocene) : north of Birket-el-Qurun. 



Shill (PI. XX. figs. 1, 1 A, 1 B ; text-fig. 64). — The type skull is not quite complete, 

 the zygomatic arches and a portion of the basal region of the cranium being lost. The 

 occipital surface is high and broadens out from above downwards. The occipital 

 condyles (cond.) are larger and more prominent than in any other Sirenian skull 

 with which comparison has been made, except Eotherium ; they are almost pedunculate 

 and their articular surface is strongly convex from above downwards and extends 

 considerably on their ventral face. In the mid-ventral line they are separated by a 

 deep rounded notch ; but it cannot be determined what share, if any, the basioccipital 

 took in their formation, the sutures being obliterated. 



Above the foramen magnum the eccoccipitals {exo.) meet in a suture about 2-3 cm. in 

 length, thus completely excluding the supraoccipital from the opening : their upper 



* Quai-t. Journ. Geol. See. vol. xi. (1855) p. 541. 



t Zigno, "Sirenii fossili trovati nel Veneto," Mem. 1st. Veneto d. Sci. vol. xviii. (1875) p. 445; also by 

 the same author, " Quelques Observations sur les Sireniens fossiles," Bull. Soc. geol. Erance, [3] vol. xv. 

 (1887) p. 728, 



