ME. A. W. WATEES ON MEMBEANIPOEIDiE. 679 



Membeanipoea Laceoixii, Aud. Sf Bush. (PI. 48. figs. 14, 15.) 



Memlaranipora Lacroixii, Busk, Brit, Mus. Cat. Mar. Polyz. p. 60, 

 pi. Ixix. figs. 1-3 ; Hindis, Brit. Mar. Polyz. p. 129, pi. xvii. figs. 5-8. 



Busk was the first to refer the British species to Audouin's 

 figure, but I am uot quite sure what was meant by Audouin, 

 and have not seen anything from, the Mediterranean which, 

 according to the methods adopted in prej)aring this paper, corre- 

 sponds with the English form. Audouin's figure may have 

 ] epreseuted a specimen of M. crassionarginata in which no ovi- 

 cells or avicularia were found, and frequently in considerable 

 pieces of that species none occur, and it is very easy to be misled 

 by such a specimen. 



Pergens put M. Lacroixii under M. reticulum, L. This may 

 Lave been the species Linne had before him, but none of the 

 early descriptions assist us in identification, as there are many 

 species which would just as well fall in with the meagre diagnosis, 

 aud the figure given by Esper is equally useless. 



Busk says the M. Lacroixii and M. Savartii are synonyms, 

 and Pergens also places them both under reticulum, but we now 

 know that the rosette-plates and growth of these two species are 

 quite diff"erent. It is possible that a fuller study of a series of 

 M. Savartii may bring out new points. In spite cf doubts it is 

 proposed to retain, for the present, the name Lacroixii for the 

 species described by Busk. 



The dorsal surface of the British M. Lacroixii is very charac- 

 teristic (PI. 48. fig. 14). In the calcareous basal wall near the 

 distal end there is on each side a transparent circle, and some- 

 times there are other small ones, and the lateral walls throw out 

 irregular projections, while on the distal walls there are two 

 projections opposite those on the next zooecium (fig. 14). 



The interesting point about this is that specimens from New 

 Zealand correspond in all these minute particulars. It seems to 

 be fairly common from New Zealand, and some spinous specimens 

 of Lacroixii were at first placed under M. lineata, a species 

 which I now believe to be only a northern form. 



The operculum has a membranous extension beyond the 

 chitinous arch (fig. 15), and in this respect is similar to that 

 of M. Mans and M. Mans var. ocellata, W. As shovrn by 

 Pergens, the shape and size of the zooecia are subject to great 

 variation. 



Loc. Britain, New Zealand, and fossil. 



48* 



