MOLLUSCA. 



IV.-NUDIBEANCHIATA. 



(1 Plate.) 

 BY SIR CHARLES ELIOT, K.C.M.G., LL.D., Vice- Chancellor of the University, Sheffield. 



THE Nudibranchiata collected by the ' Discovery ' consist of the following species : 



*1. Tritonia challengeriana Bergh. 



*2. Tritoniella belli. Gen. et spec. nov. 



3. T. sinuata. Spec. nov. 



4. Bathydoris hodgsoni. Spec. nov. 



5. B. inflata. Spec. nov. 



6. Doto antarctica. Spec. nov. 



*7. Notaeolidia depressa. Spec. nov. 



8. Cuthonella antarctica. Spec. nov. 



9. C. paradoxa. Spec. nov. 



10. C. modesta. Spec. nov. 



11. ? Cratena sp. 



12. Galvinella antarctica. Gen. et spec. nov. 



All the above forms are represented by a single specimen except Tritoniella belli, 

 of which there are five. Three minute Aeolids stated to have been with No. 1 1 have 

 been lost. The bottle was broken, and only the remains of one specimen were found. 



Many of the specimens appear to be well preserved, but, in addition to the 

 changes in colour and shape which usually affect Nudibranchs kept in alcohol, they 

 have undergone exceptional vicissitudes, such as being frozen into solid lumps when 

 first taken out of the sea. It is therefore not surprising if the external appearance has 

 been altered in some cases. A superficial examination of the specimens of Tritoniella 

 belli suggests that they comprise three species of very different shape, but as the 

 anatomy is identical and the naturalists who saw the living animals regarded them as 

 all of one species there cannot be much doubt that the differences are due to distortion. 

 The real appearance of such forms as Bathydoris hodgsoni must remain a matter of 

 doubt, and the species can be safely defined only by anatomical characteristics. 



I have some doubt as to the reality of the distinction between Tritoniella belli and 

 T. sinuata, and between Bathydoris hodgsoni and B. inflata. The differences, both 

 external and internal, are sufficient to provide specific characters, but it is possible that 

 these characters may really be due to the state of preservation and to age, the second 



* Of these species only are there any specimens in the Museum^ivailable for investigation. ED. 



