1897] NOTES AND COMMENTS 223 



The Sirenian Mammals 



The want of all definite knowledge of the ancestry of the 

 Tertiary land-mammals is strange. Our absolute ignorance of the 

 origin of the marine mammals like the whales, dolphins, and sea- 

 cows is still stranger. Marine deposits of the Cretaceous and early 

 Eocene periods are recognised nearly all over the world, but not a 

 trace of the Cetacea and Sirenia has been found in them. So far as 

 known, these curious types appear fully evolved at the top of the 

 Eocene. 



Nor does embryology help us much. It has shed a little light 

 upon the nature of the Cetacea ; we might therefore expect some 

 information from this source concerning the Sirenia. Thus far, how- 

 ever, the results are small, and Prof. Willy Kukenthal's new memoir 

 on the Sirenia (in Semon's " Zoologische Forschungsreisen in Aus- 

 tralien und dem Malayischen Archipel," vol. iv., lief. 1), which is 

 one of the most important monographs issued during the past month, 

 does not contribute much to the solution of the great problem. 

 The available material, it is true, is small — only four stages of 

 Halicore and six stages of Manatus — and only three chapters 

 (external form, integument, and dentition) are published. It is a 

 most important contribution to the facts of the case, and for this 

 alone we must at present remain grateful. 



The Origin of the Irish Fauna 



Not only is it almost impossible as yet to fathom the mysteries 

 connected with the dawn of the present order of things in the dis- 

 tribution of life on the various land-areas ; it is very difficult to 

 discover the routes of the migration and distribution of organisms 

 even during comparatively modern periods. During the last few 

 years, however, much attention has been paid to the relations of the 

 existing faunas and progress made in the determination of their 

 affinities. Among others, many Irish naturalists have discussed in a 

 very interesting manner the relations of the fauna of their island, 

 and have arrived at various conclusions, some of which may prove 

 to be of permanent value. 



Quite recently Dr E. F. Scharff, Keeper of the Natural History 

 Collections in the Dublin Museum, has returned to the subject, and 

 published an interesting paper in the Proceedings of the Eoyal 

 Irish Academy (ser. 3, vol. iv., No. 3, 1897, pp. 427-514). The 

 contribution is lengthy, and it is written in a somewhat disconnected 

 style ; and how the author gets from his premises to his conclusions 

 is not always apparent. Dr Scharff argues that part of the Irish 

 fauna lived in Ireland in pre-glacial times ; that the lower con- 



