232 SIDNEY P. HARMfiR. 



M. delicatissima constantly occurs; the fragment being, 

 moreover, from the locality (King George's Sound, West 

 Australia) from which Busk records the Polyzoon. The Alga 

 is, curiously enough, covered by Membranipora bicolor, 

 Hincks,^ which appears at first sight to correspond with 

 Busk's description of M. delicatissinia. I find the expla- 

 nation of this discrepancy in two specimens (co-types, from 

 King George's Sound) of Amansia pinnatifida in the 

 University herbarium at Cambridge. One of these is 

 covered by M. bicolor, and the other by M. delicatis- 

 sima, both being strikingly alike when seen without magni- 

 fication. 



M. delicatissima (figs. 42, 43) should clearly be placed 

 iu the genus Siphonoporella. The first impression pro- 

 duced by its appearance is that it is a spineless Membrani- 

 pora, with a large ''aperture" occupying nearly the whole 

 of the front surface, and filled by a transparent membranous 

 ectocyst, in which lies the small operculum. A small portion 

 of the front wall is calcareous, immediately on the proximal 

 side of the aperture. The calcareous cryptocyst descends 

 with a uniform slope from this region, and thus has no hori- 

 zontal proximal portion as in Steganoporella. At about 

 the middle of the length of the zooecium the cryptocyst meets 

 the basal wall on one side, while from the other side a well- 

 developed tube projects into the subopercular portion of the 

 body-cavity. This tube is so asymmetrical that the cavity of 

 the zooecium which is roofed by the cryptocyst is retort- 

 shaped, the junction of the tube with the cryptocyst being iu 

 some cases a little complicated. The pi'oximal division of 

 body-cavity overlaps the base of the tube on one side, and in 

 some cases (as in figs. 42, 43) on the upper side as well. 

 The tube on the other side springs directly from the lateral 

 wall of the zooecium, and below from the basal wall along 

 the line z. The consequence of this arrangement is that the 



^ 'Ann. Mas- Nat. Hist.' (5), vii, 1881, p. 148. The species is probably 

 nearly related to Siphonoporella, although perhaps not actually to be 

 referred to this genus. 



