Adeonella (Laminopora) contorta, (fee. 497 



The first I would call the biccUular antl the second the 

 mullicellular ovaria, though, as the multicellular forms may 

 pass through a stage somewhat like the bicellular, it must be 

 presumed that sufficient material is available before stating 

 to which f;rou[> ovaria belong. In Btujula the ovarium is 

 bicellular and is formed at the proximal end near to the 

 caecum, passing into the ovicell when quite small. In 

 Scrupocellaria the ovarium is multicellular and near the 

 distal end, with some of the ovarian cells very large. Some 

 forms, recently removed from Bugula by Levinsen, have the 

 multicellular form, showing by this that they are not so 

 closely allied to Bitgula as was previously supposed. There 

 are other genera in which the study of the ovaria is going to 

 give us some classificatory assistance. 



The Adeonidae in its fullest sense is a most important 

 group in the Tertiary and Cretaceous periods, as I have seen 

 in the examination of my Cretaceous collections, and a study 

 of llagenow's and other plates suggests that a large number 

 belong to this group, though in but few is there any difTerence 

 in the size of the gonoecia and other zooecia. 



There are gonoecia in the fossil Foi'iceUa*, Canu ; in 

 Smittislomaj Canu, Schizostoma, Canu, Calvetina, Canu ; 

 also in the family Meniscoporida?, including Portstoma, 

 Canu, Meniscopora, Gregory : but although an external 

 difference in size of the ordinary and gonoecial zooecia has 

 been seen in some species of Adaonellidas and its allies, both 

 recent and fossil, it must be repeated that in very many no 

 difference can be found, and this is the case in many Chalk 

 fossils which will probably be found to belong to the 



group t. 



It is a noticeable fact that as we go back in the geological 

 record the number of genera with external ovicells becomes 

 much less numerous, in the Tertiaries the Adeonellidie and 

 Meniscoporidse with gonoecia were largely represented, as 

 were also the Onychocellidge, which have an internal sac for 

 the development of the embryo, also their ally Cellaria has 

 no raised ovicell. In the Cretaceous the number with external 

 ovicells is si ill more reduced. The older workers were not 

 as keenly on the lookout for ovicells as a useful classificatory 

 character as we are, but that is by no means the chief reason 

 ■why so iQ,\w have been described fossil. 



* " Bryozoaires des teiTains tert. des env. de Paris," Ann. de Pal^ont. 



vol. ii. p. 46 (1907) ; and Etude des Brv. Tert de la Tunisie, p. 28 



(190.1). 



t Tlie common Tertiary '^ Eschar a'' monilifera has g-onoecia. 



