Renews — Br. 0. Abel — Fossil 8irenia of Austria. 329 



fragments of them already mineralized, thus forming the ore deposits 

 surrounded by the granite-porphyry. The crystallization of that 

 rock then became complete, after which the mass was elevated 

 and exposed to denudation during the formation of the Devonian 

 rocks, and at later periods was affected, as described, by other earth 

 movements. The explanation is not without its difficulties, which 

 cannot be stated in a few words, but that does not affect the value of 

 the treatise as a conscientious piece of work, and a history of a very 

 remarkable mineral deposit. T. G. B. 



III. — Dr. 0. Abel. Fossil Sirenia of Austria. 



Die Sirenen der mediterranen Tertiarbildongen Osterreichs. 

 — Abhandlungen der k.k. Geologischen Eeichsanstalt. Bd. xix. 

 Heft 2, pp. 1-223, with 7 plates and 26 text -figures. 

 (Vienna, 1904.) 



THIS is perhaps the most valuable memoir on the Sirenia that has 

 appeared for some years, for although from the title it might be 

 supposed to deal only with the fossil Sirenia from the Austrian 

 tertiaries, this is far from being the case. The author first discusses 

 in considerable detail the limits of the genera HalitTierium, 

 Metaxytherium, and Fehinotherium, and describes the peculiarities of 

 their skeletons and teeth. He points out that these genera are 

 a succession of forms passing more or less one into the other. 

 Halitherium ranges from Upper Eocene to Lower Miocene, 

 Metaxytherium from Lower Miocene to Pliocene, while Felsinotherium 

 is confined to the Pliocene. In the second part of the memoir the 

 writer describes in detail remains of Halitherium Christoli, Metaxy- 

 therium Krahuletzi, and M. Petersi from the Austrian Miocene. 



The third part of the memoir is perhaps the most valuable and 

 interesting. It consists of a discussion of the modifications of th© 

 Sirenian skeleton from the earliest known forms from the Middle 

 Eocene of Egypt to the types still existing. Each of the important 

 parts of the skeleton is considered in turn, and it is shown that 

 in each there has been a gradual modification in a definite direction. 

 Thus the earliest types possess a full set of incisors and canines 

 which disappear in the later forms, their place being taken by the 

 horny covering of the front of the jaws, though in some cases a pair 

 of tusks, probably equivalent to the second incisors, may persist. 

 In the molars there is a gradual increase of complexity resulting 

 from the addition of secondary tubercles to a primitively bilophodont 

 tooth, each transverse crest of which consists of a pair of cusps. 

 Still more important are the changes that are shown to take place in 

 the pelvis. For the first time the author figures and describes 

 a Sirenian pelvis in which all the elements are complete, the 

 obturator foramen being entirely enclosed by the ischium and "pubis 

 as in ordinary land mammals. This primitive form of pelvis is 

 found in JEotherium from the Mokattam Limestones (M. Eocene) 

 of Cairo, a Sirenian first described by Owen from the cast of 

 a cranial cavity, and its discovery is a great step towards bridging 

 the gulf between the Sirenia and their terrestrial ancestors. 



