13° SMITH : A NEW SPECIES OF ACROPTYCHIA. 



apertures of the Ascidian colony. I did not notice the Lamellaria 

 until I had accidentally partly dislodged it in detaching the 

 Leptodinum from a stone. I then pointed it out to a couple of 

 naturalists who were with me, and we were all much struck with the 

 difficulty in detecting it when in situ on the Ascidian. 



This is clearly a good case of protective colouring. Presumably 

 the Lamellaria escapes the observation of its enemies through 

 being mistaken for a part of the Leptodinum colony ; and the 

 Leptodinum being crowded like a sponge with minute sharp-pointed 

 spicules is, I suppose, avoided as inedible (if not actually noxious 

 through some peculiar smell or taste) by carnivorous animals which 

 might devour such things as the soft unprotected mollusc. But the 

 presence of the spicules evidently does not protect the Leptodinum 

 from Lamellaria, so that we have, if the above interpretation is 

 correct, the curious result that the Lamellaria profits by a protective 

 characteristic of the Leptodinum for which it has itself no respect, 

 or to put it another way, the Leptodinum is protected against 

 enemies to some extent for the benefit of the Lamellaria which 

 preys upon its vitals. 



DESCRIPTION OF 

 A NEW SPECIES OF ACROPTYCHIA. 



By EDGAR A. SMITH, F.Z.S., 

 Zoological Department, British Museum, London. 



1 PI. 1. figs. 1 to 4.) 



Last June I had the privilege of describing in this Journal 1 a very 

 remarkable form of Aeroptyehia and of making some observations on 

 the other species belonging to the genus. I now have the pleasure 

 of characterising another new form, the. fourth belonging to the 

 group. Like the known species, this also comes from Madagascar, 

 where it was collected by the Rev. W. Deans Cowan, at Mahanovo. 



Aeroptyehia albocincta. 



(PI. 1. figs. 1-2.) 



Testa turbiuata, eonstricte umbilicata, fusco-olivacea, ad 

 peripheriam linea pallida cincta; aufractus 6 convexi, regulariter 

 et sublente accrescentes, striis spiralibus tenuibus numerosis 



1 The " Conchologist," 1892, vol. ii., pp. 22-23. 



