212 LIVERPOOL BIOLOGICAL SOCIETY. 



plate are called " portion of a band of elongated mesoder- 

 mal cells found accompanying a skeleton fibre." 



I have mentioned already the great similarity which 

 exists in the external appearance of Axinella mammiWtta 

 and Polymastia mammillaris. As it might be misleading 

 to distinguish the species by the spicules alone, as those 

 of Axinella mammillata sometimes approach the tylostylote 

 character, and those of Folymastia mammillaris the tylote 

 character, it appeared quite necessary to sectionize one of 

 the papillae for the sake of identification. The difference 

 then is quite striking. In Polymastia mammillaris the 

 papilla has the form of a tube with a large central cavity, 

 with large subdermal spaces and well developed pote- 

 membranes.* None of these characters are present in 

 Axinella mammillata. Inside of the papillae we have here 

 and there larger or smaller quite irregular cavities, no 

 distinct subdermal spaces, and of oscula, pores and pore- 

 membranes nothing definite could be seen. 



I found one specimen of this new species in one of the 

 tidal pools on the north end of Puftin Island, at low^est 

 tide, April, 1889. 

 Raspailia ventilahrum, Bowerbank. 



Dictyocylindrus ventilahrum, Bowerbank. 



In my previous report I regarded this species as identi- 

 cal with Raspailia viminalis, Schmidt, and described it 

 under that name. But, as pointed out recently by Top- 

 sent,! there exists a difference between P. viminalis, S., 

 and P. ventilahrum, B. The styli are slightly tylostylote 

 in R. viminalis, whilst in R. ventilahrum they are of the 

 normal character. 



* See my former Report in Proc. Liverpool Biol. Society, vol. iii., pi. vi., 

 figs. 2 and 3. 



t lijjnile Topsent, " Etndes de Spongiaires." Revne Biologique du Nord 

 de la France, tome ii., no. 8, Mai, 1890. 



