524 MR. A. W. WATERS ON 



same as Busk's ' Challenger' jR. hirsuta, have besides minute cir- 

 cular avicularia round the fenestrse, also on the inner side of each 

 of the zooecia bordering a fenestra., an elongate avicularium with 

 the beak bifurcate but with an acute mandible. This was de- 

 scribed by Busk for B. hirsuta and is one of the most important 

 characters. Large pieces were examined without finding any of 

 the long antenniforin spines described by Busk, and then in 

 some places they were found in abundance. This is much like 

 R. monilifera var. umbonata MacG., but in that there are only 

 occasionally the long bifid avicularia on the zooecia bordei'ing on 

 the fenestrse, and they must be separated because, among other 

 reasons, the branches have more zooecia in A*, umbonata ; the 

 more delicate hirsuta is a tropical form, whereas umbonata is 

 Australian. 



The mo)iilifei^a group of Retepora seems to be well defined, and 

 perhaps should have generic value given to it. All have the 

 well known " trifoliate stigma " on the ovicell, and in most there 

 is a minute avicularium on the lip to one side ; the opercula 

 genei^ally are fairly similar with a nearly straight proximal edge, 

 and in shaj)e rather wider than long, with the muscular attach- 

 ments rather high up and near the border. In R. formosa 

 MacG. and R. contortitplicata B., the operculum is more curved 

 on the proximal edge, and no labial avicularia have been found 

 in these ; apparently all have the labial pore, which is often tlie 

 end of a long tube opening into the zocecium * proximally to the 

 operculum, and I agree with Jvillien and Calvet in speaking of 

 this as the Reteporidan pore, as it is characteristic of a lai-ge 

 number of ReteporcB. 



There is another group with widely open ovicells, and in these 

 none have a labial avicularium, unless R. incrustata Calv. belongs 

 here ; the proximal edge of the operculum is not straight, and in 

 some it is contracted in the middle like the opercula of some 

 Lepralia (for example L. hippopus Sm.). In this group are 

 R. imjierati B., R. elongata Smitt, R. tessellata Hincks, R. solan- 

 de7-ia Risso, R. inordinata Calv., having a broad thickened border; 

 while R. sinuosa Kirkp., R. novcezelandioi Waters, R. hippocrepis 

 Waters, R. gelida Waters, R. lepralioides Waters, have longhands 

 at the sides of the operculum, for the muscular attachments, and 

 lateral contraction of the oral aperture. The Reteporidan pore 

 has only been observed in this group in R. solanderia Risso. 



Another group has a fissure in the ovicell as in R. celhdosa L. 

 and the proximal edge of the operculum is nearly straight, and 

 very similar throughout this group, labial avicularia occur in 

 some but not in all. There are a few Reteporce with imperforate 

 ovicells. Throughout the genus the oral glands are very well 

 developed. 



The minute round or oral avicularia with thin membranous 



* Waters, " Medit. & New Zeal. Reteporidse," Jonrn. Linn. Soc, Zool. vol. xxv. 

 pp. 255-6 ; Exped. Aiitarct. Beige, pi. vi. fig. 6 a (1904). 



