R. 21. Brydone — Neiv CJudk Polyzoa. 345 



Almost all ossiferous cave-deposits are formed in either one of two 

 ways : — 



1. The caves have been the haunt of predatory animals or man, 

 who not only left their own remains in the cavern, but also those of 

 the animals brought in as the spoils of the chase. 



2. Or the remains have been introduced and accumulated through 

 the agency of water. 



I believe that all the Balearic cave-deposits have been accumulated 

 in the latter manner, and, further, that all are now approached by their 

 original terminal end.^ This would help to account for all having 

 been found on the coast, for here the action of the sea and in some 

 cases alteration of the coast-level have aided and accelerated 

 "weathering. Thus cliff faces may be worn and broken away, leaving 

 exposed underground channels and chambers with their accumulated 

 contents. A continuation of this same work of destruction added to 

 rapid weathering is sufficient to account for the very generally 

 fragmentary state of the deposits. This last might partially explain 

 the paucity of species. The remains may have been introduced into 

 the caves as either skeletons or carcases, and it is the lattei', no doubt, 

 which account for the finding of associated skulls and mandibles and 

 other bones. Similar conditions to the above have been observed by 

 the writer in many Pleistocene cave-deposits of other islands of the 

 Mediterranean. 



II. KOTES ON NEW OK IMPEIiFECTLY KNOWN ChALK PoLYZOA. 



By R. M. Brydone, B.A., F.G.S. 



[Continued from the March Ntcmber,p. 99.) 



(PLATE XXVI.) 



rr^HE group of Jleuibranipora, with a small median barred 

 JL avicularium placed immediately above the ooecium, of which 

 If. Grijfii/u', Bryd., is a leading instance, contains several Senonian 

 members in addition to the Trimingham forms (M. Triminghame7isi8, 

 If. anterides, M. humiliata) which I have already described in this 

 Magazine. They seem to arise first in the zone of Ificraster 

 cor-anguinuin. 



Membranipora simulacrum, sp. nov. (PI. XXVI, Figs. 1, 2.) 



Zoarium unilaminate, always adherent. 



Zooecia large, very slightly subpyriform, areas oval, with average 

 length -5 to -55 mm. and breadth '3 mm.; side walls bent slightly 

 inwards, and so low and slender that at a hasty inspection they 

 might be taken to be mere ghosts of some S2)ecies with a low arched 

 front wall. 



Ocecia very generally present in mature zooecia, and of circular 

 ground plan ; I have not met with a perfect specimen. 



Avicularia of two kinds: (1) The characteristic accessory type: 

 these are shuttle-shaped with rounded ends, and have an aperture of 



' See the present writer's Kotes in Cavqnnfj in Crete (A. Trevor-Battye), 

 p. 245, London, 1913. 



