or Little Known, Polyzoa. Ill 



sinus. There are also other round or elliptical avicularia 

 scattered in various parts, and numerous avicularia, with 

 long narrow mandibles closing in bidentate rostra, close 

 to the edge of the fenestras. Similar avicularia occur in 

 some other species, but in these, so far as I have seen, they 

 always open horizontally inwards, while in the present they 

 are directed across the edges of the fenestras. The vertical 

 slit, the closure of which gives rise to the ridge on the 

 ovicell, is still in some instances slightly open towards the 

 upper extremity. 



R. fissa, M l G. 



The description and figures of this species given in my 

 last paper were taken from the original specimen, which is 

 of considerable size and well calcified. I have a number of 

 other specimens with the fenestras more elongated, the inter- 

 spaces narrower, the cells longer, and the peristome very 

 much produced, of the true position of which I was doubtful. 

 I am now satisfied that they belong to the same species, and 

 I believe that they are identical with Smitt's Floridan, R. 

 marsupiata, although they do not altogether correspond 

 with his description, and that they are probably the 

 Australian form referred to R. cellulosa by Busk and 

 Hincks. 



In this form the fenestras are large, elongated, and wide, the 

 interspaces narrow, with one to four rows of cells. The cells 

 are long, narrow, separated by well-raised margins. The 

 peristome is much produced, curved forwards, with a nearly 

 circular aperture opening upwards. From the centre of the 

 lower lip a shallow groove, with slightly raised edges, 

 extends vertically downwards ; immediately below this, or 

 slightly to one side, is usually an avicularium with a bluntly- 

 triangular mandible directed downwards and tilted some- 

 what forward. The lower lip on either side of the groove 

 is smooth or sometimes serrated. The edges! of the groove 

 occasionally meet to form a tube either extending the whole 

 length or confined to the lower end. Occasionally the small 

 avicularium is enormously developed with a large triangular 

 mandible. There are also sometimes other avicularia. In 

 some cells the avicularia are entirely absent. The ovicells 

 are rounded with a vertical slit. In different specimens a 

 complete gradation may be seen to the structure of the 

 typical R. fissa. 



