NO. 8 INTERRELATIONSHIPS OF THE CETACEA WINGE 65 



it at first to the Squalodonts, later he put it in a separate family. It 

 plays an important part in Abel's studies of cetacean descent, whether 

 rightly or not time will perhaps tell ; meanwhile the genus is altogether 

 too slightly known for anything positive to be built on it. 



Eocctus described by Fraas (first called Mcsocetus Fraas, not of 

 Van Beneden, not of Moreno) is thought to be a connecting link 

 between Protocctus and Zcuglodon, with long vertebrae. The remains 

 are still too uncertain for judgment to be passed. 



" (P. 19.) Kiikenthal (Vergl. -anat., etc., Unters. an Walthieren ; 

 Denkschr. medic, -naturw. Ges. Jena, vol. 3, pt. 2, 1893, P- 291) thinks 

 that the bone in the hand of Balcvna mysticetus, which is ordinarily 

 regarded as a remnant of the first finger, a first metacarpal, is not 

 that, but a finger before the first finger, a prccpollcx, in spite of the 

 fact that the same bone in Balccna austral is (as can also be seen in two 

 skeletons in Copenhagen) may bear two well-developed phalanges, 

 something that is not elsewhere seen in any "" pra:pollex." As to the 

 longest finger, which is usually reckoned as the third, he believes that 

 it is not the third but the second, and that the third is absent. The 

 reason for this remarkable interpretation is probably a desire to find 

 agreement with Balccnoptcra, in which he thinks he has proved that 

 the third finger is the one which is absent, and not the first as is gen- 

 erally supposed. If the first finger were present in Balccna in a more 

 or less atrophied condition, it would be reasonable to suppose that it 

 was this finger which is absent in the nearly related Balccnoptcra, 

 which has only four digits ; but that belief Kiikenthal will not allow. 

 Occasionally he has found in Balccnoptcra musculus something re- 

 sembling a few atrophied phalanges lying loose in the palm between 

 the fingers that are usually called the third and fourth. These 

 structures Kiikenthal regards as remnants of the third finger and 

 thus to be proof that it is the third finger which is absent in the 

 tetradactylous hand. Protest against Kiikenthal's interpretation has 

 already been made by Braun and Kunze (see Kunze, Zool. Jahrb., 

 Abth. f. Anat., etc., vol. 32, 191 2, pp. 639-641). There can be no 

 doubt that there is here a case of malformation, a supernumerary 

 digit, a kind of doubling of one of the fingers. Tendencies in this 

 direction are indeed not rare in cetaceans, which on the whole show 

 great indifference as to details in the structure of their abnormal hand. 



"(P. 21.) On the Balsenidse see especially (Of the numerous works 

 that deal with cetaceans there are many others that might have a 

 claim to be mentioned. The choice that has been made here and in 

 the corresponding lists for other families is somewhat arbitrary. 



