F. jD. Longe — Oolitic Polyzoa. 27 



family Urceolata. But it is clear that the only reason of which he 

 was aware for separating these ambiguous Escharoid forms from the 

 rest of the Esclim-idcB was that, according to the authority of Milne- 

 Edwards, the Diastoporiclce had no opercula, and therefoi'e must have 

 belonged to the other famil^^ or order. It may be observed that he 

 had not ascertained this himself, for he had actually classed Biastopora 

 with the Urceolata. But had Hagenow examined the recent Diasto- 

 poridce for himself, he would have found that while they present a 

 corresponding irregularity of cell feature to that of the Escharoid 

 forms, which Milne-Edwards and Jules Haime assigned to the same 

 genus, they exhibit operculoid lids in many of the cells, punctured 

 in a similar manner to those which D'Orbigny observed in the forms 

 which he classed as Eleida. Why are not these lids opercula ? I 

 submit that there is absolutely no reason for disputing their complete 

 homology with the opercula of the Cheilostomata, except that the 

 absence of such an apparatus in the mouth of the cell has been put 

 forward (apparently on the authority of early observers) as the 

 principal feature by which the Ci/clostomata are distinguished from 

 the Cheilostomata. 



How the lids which close some of the cells in Biastoporidce were 

 either not observed or their presence ignored b}' early systematists 

 is easily explained. According to the definition of the Tubuliporina 

 given by Johnston,' which, with an immaterial modification, has 

 been adopted by Busk, the absence of opercula is stated to be an 

 essential characteristic. The Cyclostomatous cell is defined in 

 Busk's Synopsis of the Primary Divisions of the Polyzoa.^ to be 

 " tubular, orifice terminal, of the same diameter as the cell, with- 

 out any movable apparatus for its closure." 



Now it is perfectly true that the more prominent and visible cells 

 in the Biastoporidce are of the typical tubular form as above defined, 

 and they sufficiently demonstrate the connexion between Biastopora 

 and other tubular-celled forms for the purpose of classification. It 

 is, however, very clear that nearly every coenoecium, particularly of 

 B. patina, Busk, contains other cells of a very different character 

 and pattern, so much so, that the observation of a few specimens 

 will show that this definition of the cyclostomatous cell only 

 applies to some of the cells in this form. It will be observed that 

 besides the prominent tubular cells, there are some cells decumbent 

 and much immersed, which have a fusiform or elongated oval shape, 

 and that these cells are closed by lids or shutters of the same form 

 and character apparently as the opercula in many of the Lepralidm.^ 

 To these cells this definition does not apply any more than to the 

 cells of many of the Cheilostomatous forms. 



Although these closed cells appear to have been unnoticed by 

 earlier observers, they have not escaped the observation of later 

 students. Professor Busk himself recognizes their existence in 

 Biastopora patina ; and Mr. Hincks mentions them as occurring 

 in this and other species of living Biastoporidce. Johnston, however, 



> Johnston's British Zoophytes, vol. i. p. 262. 



2 Preface to the Fossil Polyzoa of the Crag, p. 9. ^ gee Fig. 8. 



