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VI. —The Anatomy of a New Species of Bathydoris, and the Affinities of the 

 Genus : Scottish National Antarctic Expedition. By T. J. Evans, M.A. (Oxon.), 

 Lecturer in Zoology in the University of Sheffield. Communicated by Dr J. H. 

 Ash worth. 



(MS. received October 3, 1913. Read January 19, 1914. Issued separately April 1, 1914.) 



[Plates XVII. and XVIIL] 



Introductory. 



The genus Bathydoris was created by Bergh in 1884 in his Eeport on the 

 Nudibranch Mollusca collected by the Challenger. In his account of the anatomy 

 of the new genus Bergh draws attention to the anomalous combination of characters 

 possessed by the animal, and gives it an annectent position between the Dorids and 

 the Tritonids, but places it among the Dorids on account of the predominance of Dorid 

 features. The single specimen of Bathydoris abyssorum was dredged off New South 

 Wales in 2425 fathoms. A second specimen of this peculiar genus was obtained by 

 the Danish Ingolf Expedition and described by Bergh in 1900. This specimen came 

 from 1870 fathoms in Davis Strait, and resembled B. abyssorum, with specific 

 variations. Thus Bathydoris came to be regarded as an isolated genus with the 

 characters of a connecting link, and appropriately a denizen of deep water. Our 

 anatomical knowledge of the animal is derived almost entirely from Bergh's accounts 

 of the two species mentioned, and is moderately extensive, considering the rather 

 imperfect state of preservation of the material and the fact that he was dependent on 

 single specimens in each case. 



Two more specimens were brought from the Antarctic by the Discovery and 

 described by Sir Charles Eliot in the Report of the National Antarctic Expedition 

 published by the Natural History Museum in 1907. These constituted separate 

 species resembling Bergh's, but their state of preservation was such that Eliot was 

 able to add little to our knowledge of the anatomy of Bathydoris. The discovery of 

 one of Eliot's species in 100 fathoms dispels the idea that the genus is confined to 

 the great depths. 



A specifically distinct specimen was also taken by the German Antarctic Expedi- 

 tion, but Thiele, in the Report on the Mollusca recently published, confines himself 

 to a superficial description in order to retain the rare animal intact as a museum 

 specimen. 



It would seem to be the fate of polar expeditions to bring back single specific 

 specimens of this genus ; for the species which forms the subject of the present 

 memoir is based on one specimen dredged in 1410 fathoms by the Scotia in March 

 1904. When the zoological material of the Scottish National Antarctic Expedition 



TRANS. ROY. SOC. EDIN., VOL. L. PART I. (NO. 6). 26 



