84 



CETACEA 



ORDER IV 



Suborder A. ARCHEOCETI Flower. 



External nostrils opening forwardly and upwardly and situated on the upper 

 side of the snout. Nasals short. Maxilla not extending over the fronfals. Teeth 



in premaxillary, niaxillary and man- 

 dible ; the anterior teeth with one root, 

 the posterior with two, and in the upper 

 jaw fregiiently with three roots. 



Family 1. Zeuglodontidae.i 



Head elongate, brain -case small, 

 temporal fossa widely extended, sagittal 

 crest well developed. Parietals elongate, 

 narrow and forming part of cranial roof ; 

 frontals broad and short, roofing over the 

 orbits. Zygomatic arch rod-like. Snout 

 long and compressed. Nasals long and 

 narrow. Mandible long, low and without 

 well-defined symphysis. Teeth differ- 

 entiated : ' ' ' ' , and complete milk 



dentition present. Front teeth I-^-P^ 

 (incl.) separated; the back teeth very 

 compactly set. I, C and frequently P^ 

 all conical with one root ; hind teeth ivith 

 two roots. P.2 to P^ have cusps on the 

 front and rear edges and M has a few on 

 the back edge. The two hind upper P, at times also 

 the upper M, are three-rooted. The cervical vertebrae 

 are short, not fused together. Usually twelve dorsal 

 vertebrae; the last of these, as well as the lumbar 

 vertebrae, are frequently very much elongated. Caudal 

 vertebrae are short. Ribs with two heads. Scapida 

 broad and with acromion, coracoid process and rudi- 

 mentary spine. Humerus short, with massive deltoid 

 crest and well-developed trochlea. Badius in front of 

 ulna, with two distal articular surfaces. Pelvis and 

 femur rudimentary. Sternum composed of several 

 pieces. Possibly dermal armour was present. 



Protocetus Fraas. f M. The two last P only 

 with one rear cusp, M also with front cusps. C-P^ 

 indistinctly two-rooted, P^ to iiP each with three 

 roots. Vertebrae small, like those of carnivores. 

 Middle Eocene ; Mokattam, Egypt. P. atavus Fraas. 



1 Andrews, C. W., Pappocetus. Proc. Zool. Soc, 1919.— J^mas, E. , Neue Zeuglodonten aus dem 

 Mitteleozaen von Mokattam. Geol. -Palaont. Abliandl., vol. x., 1904.— Zttcfts, F. A., Notes on the 

 Osteology of Zeuglodon. Auier. Naturalist, IS95. —iluUer, Joh., Uber die fossilen Reste der 

 Zeuglodonten von Nord-Amerika, Berlin, 1894. — Stromer, E. v., Zeuglodontenreste aus dem 

 Mitteleooaen des Fayum. Beitr. Palaont. Osterr.-Ung., vol. -xv., 1903.— Die Archaoceti des 

 agyptiscljen Eocaeus. Ibid. vol. xxi., 1908. 



Fig. 111. 



Zeiiglodon osiris 

 Dames. Upper 

 Eocene of Fayum, 

 Egypt. Skull and 

 anterior portion of 

 the body. 1/12. 

 (After Stromer.) 



