ALDliq^GA AND THE EIVER-MTJEKAT CLIFFS, SOrTH ATJSTEALIA. 289 



line along the middle of the lateral walls, and correspond with those 

 of Bifiustra delicatula, Busk, with which perhaps this species should 

 he united. 



Mr. Woods's description and figures are from the fossil upside 

 down. 



12. Membranipoea (Amphiblestefm) Michatjdtana, d'Orb. 



Gellepora Michaudiana, d'Orb. Pal. Prang, p. 404, pi. 604. tigs. 7, 

 8, pi. 712. figs. 3, 4. 



Memhrmiipora permunita, Hineks, Ann. & Mag. Nat. Hist. ser. 5, 

 vol. vii. p. 151, pi. X. fig. 2 ; MacGillivray, Trans. Eoy. Soc. Yict. 

 vol. xviii. p. 118. 



Memhranipora falcata, MacGillivray, Trans. Roy. Soc. Yict. vol. 

 ix. p. 132. 



The fossil differs from a recent specimen dredged off the coast of 

 Yictoria in having the zooecia and also the opesia a trifle smaller. 

 The avicularium of this fossil and of the one figured by d'Orbigny is a 

 little smaller than that in the recent specimens, in which it occurs 

 at the base of an abortive zooecium ; at least, this is my interpre- 

 tation of a very curious structure, but this does not seem to be Mr. 

 Hincks's view, and it is well worth further examination. In the 

 fossils the ovicells are simply rounded, without a raised rib ; and 

 this is the case in some of the ovicells of my recent specimens, while 

 others have it. 



Perhaps the recent forms should rank as M. Michaudiana^ var. 

 permunita, on account of the small zooecia to which the avicularia 

 are attached. 



Log. Eossil : Cretaceous ; Le Mans, Le Havre, Tourtenay ; Al- 

 dinga (growing on Microporella elevata). Living : off" Curtis Island, 

 Bass's Straits ; off Yictoria (on Adeona), Schnapper Point {MacG.). 



13. Membeanipoea (Amphiblestetjm) teifoliiim:. Busk, var. peo- 



PINQTTA. 



Leprcdia trifolium, MacG. Trans. Eoy. Soc. Yict. 1868, p. 9; 

 Prod, of Zool. of Yict. decade iv. p. 28, pi. xxxvii. fig. 2. 



. The fossil from Aldinga has the zooecial avicularia and globular 

 ovicells described by MacGillivray. The aperture (opesia) is about 

 the same size as that of a Crag specimen of Memhranipora trifolium, 

 Busk, in ray possession, but it differs in having a zooecial avicu- 

 larium (onychocellarium) and no other avicularia. The zooecia, in 

 shape, are very similar to those of recent Selenaria macidata^ Busk. 

 In the Eeport on the ' Challenger ' Polyzoa, Mr. Busk figures as 

 AmpTiihlestrum umhonatum (pi. xv. fig. 66) a species or variety 

 with avicularia, which is closely allied to this. 



It is strange that two forms so closely allied as Memhranipora 

 trifolium, Busk, and Lepralia trifolium, MacGiUivray, should have 

 received the same specific name when placed under different genera. 



The genus Amphihlestrum may be a convenience, but, as at pre- 

 sent defined, it cannot be looked upon as sharply separated, and 



