48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 72 



Solid ground was first reached with the discovery of Protocctus 

 atavus described by Fraas (Neue Zeuglodonten aus dem unteren 

 Mitteleocan von Mokattam bei Cairo ; Geol. it. Palseont. Abhandl., 

 herausgeg. von Koken, vol. lo, pt. 3, 1904. There could be no doubt 

 that Protocctus came from Hysenodonts and that it was itself a fore- 

 runner of the Zeuglodonts. Curiously, however, Fraas thought that 

 the origin of the Cetacea was not thereby explained. He considered 

 both Protocctus and with it the other Zeuglodonts as a side branch 

 from the carnivores which did not lead in the direction of the true 

 whales. There seems now, however, to be unanimity of opinion that 

 Protocctus, Proccuglodon, etc., are some of the long sought pro- 

 genitors of the whales. In spite of all differences from the higher 

 Cetacea there is a multitude of resemblances to them which it would 

 be impossible to explain except on the basis of relationship. One has 

 only to think of the striking likeness in such peculiarly formed bones 

 as the tympanic and scapula ; their characters in the fossils are exactly 

 those that one would expect to find in ancestral Cetacea. 



It has been said that the whalebone whales and the toothed whales 

 might have separate " diphyletic " origins ; Kiikenthal in particular 

 has spoken for this view (Ueber die Anpassung von Saugethieren an 

 das Leben im Wasser ; Zool. Jahrbiicher, Abth. fiir Systematik, etc., 

 vol. 5, 1891, pp. 373-399, especially p. 384, and elsewhere). In face 

 of the host of agreements in numerous structural relationships which 

 are found in the two groups this idea is an impossibility. Just one 

 little bone like the tympanic, with its thickened inner wall, its mussel- 

 shaped outgrowth around the outer auditory aperture, its petrous 

 process which reaches out under the mastoid, and other details, all of 

 the most peculiar form, and all essentially identical in all Cetacea, is 

 sufficient evidence of the near relationship of all whales. 



Kiikenthal has put forward a "Versuch, den Bau des Walkorpers 

 von biologischen Gesichtspunkten aus zu erklaren," most elaborately 

 in Die Wale der Arktis, Fauna Arctica, vol. i, pt. 2, 1900, section 

 pp. 181-203. 



' (P. 3.) We owe to Abel a special treatise on the skeleton of the 

 hind limb in Cetacea: Die Morphologic der Hiiftbeinrudimente der 

 Cetaceen ; Denkschr. d. math, -naturw. Klasse d. k. Akad. d. 

 Wissensch. Wien, vol. 81, 1907, pp. 139-195, with illustrations. A 

 supplement is given by Lonnberg : The Pelvic Bones of Some 

 Cetacea; Arkiv for Zoologi, vol. 7, No. 10, 1910, pp. 1-15, with 

 illustrations. 



