388 



a. B. VINE ON THE FAMILY DIASTOPOEIDiE. 



part. In fig. 19*(an enlargement of a portion of the same colony) the 

 tendency of the cells to the right and to the left is sho wn ; the other 

 figures are enlargements of special cells to show the ring-like cha- 

 racter of the mouth and peristome. There is another colony on the 

 hack of the same slab ; but this is very much worn, and the cell- 

 mouths are somewhat angular. The largest colony is on block 9 * ; 

 and it is a very interesting study. This block is a piece of coarse 

 Oolitic Limestone, much worn by attrition ; and, besides many 

 Serpulae, it contains on its surface several colonies of Polyzoa. 

 Pig. 25 is a magnified portion of a colony of D. cricopora adherent 

 to a colony of Elect (?), or one of its nearest allies, the one almost 

 wholly enveloping the other. In the fragment figured the different 

 characters of the two fossils are shown. The under one of the Eha (?) 

 type has all the cells in one plane, the walls of each cell so closely 

 connected as to leave no interspaces. The normal orifice of the 

 cell seems to be of a subcircular character ; when slightly worn it is 

 large and circular, unlike any of the cell-mouths figured by Busk 

 in his 'Crag Polyzoa' as Mesenteripora, which seems to have been 

 used as a s}monymf of Eha foil acea (D. foliacea, L&mx.). Manzoni 

 also figures J a " Diastopora " ? having a habit somewhat similar to 

 this, which he calls D. expansa, Manz. ; but the aperture is normally 

 circular with a well-developed peristome. This flat adherent type 

 of the Inferior Oolite becomes (so Mr. Longe informs me) foliaceous 

 in its after stages ; but whether it ever becomes really leaf-like with 

 cells on both sides I cannot, as yet, satisfy myself. I have no desire, 

 however, to put this type under the genus Diastopora. The other 

 incrusting form is a marginal portion of D. cricopora, having many 

 of the characters of the group, but with cells altogether at variance 

 with the general build of the true Diastopora-cell. 



The genus Diastopora has been, and is, in many instances, very 

 much abused ; and before proceeding with these studies it may be as 

 well to define and limit the genus. Lamouroux used two terms which 

 have come into general use — the one Berenicea, and the other Dias- 

 topora. Under these two names many divergent forms have been 

 placed, so that to some extent Berenicea and Diastopora are synony- 

 mous terms, the term Berenicea being used for one section of the 

 Diastoporidae and Diastopora for another section. In subdividing the 

 foliaceous Cyclostomata, Milne-Edwards formed two great groups, 

 " distinguished," says Busk, " by the character that in the one the 

 tubes are almost wholly immersed, and in the other partially free." 

 To the former group Milne-Edwards applied the appellation " Dias- 

 topoees," and to the latter that of " Tubtjlipoees." " This division is 

 natural ; but it seems convenient that it should be carried still further; 



* These numbers refer to the specimens as numbered in Mr. Longe's cabinet. 

 It would be a good thing to have the types preserved in some public museum, 

 so that they could be accessible to future students. Whenever I could, I have 

 referred to specimens so preserved. 



t D'Orb., Pal. Frang. terr. Cret. (p. 808). 



} Briozoi di Castrocaro, tav. vii. f . 83. 



