ON FOSSIL POLYZOA. 257 



Another British species is given by Haime : — 



Diastopora Lucensis (Berenicea, pi. vii. fig. 4, a.c). 



:= „ diluviana, Milne-Ed. 



=:Mt(Uisparsa Luceana, D'Orb. 



Localities. — Hampton Cliffs, Walton ; Bradford Clay and Cornbrash, 

 Laycock. 



II. BiSERiAL Diastopora, Milne-Ed. 



Mesenteripora, Blainville ; Bidiastopora, D'Orb. ; Ditaxia, Hagenow. 



It is well that the encrusting and biserial Diastopora should be sepa- 

 rated, but not widely so. In the choice of the above names I havo 

 selected the simplest — Blastopores biserialaires of Milne-Edwards — because 

 it has the precedence of the Bidiastopora of D'Orb. Busk — in the ' Crag 

 Polyzoa'and in the ' Brit. Mus. Cat.' pt. iii. — has chosen Blainville's 

 name for this division of the group. 



My chief objection to Blainville's term for the biserial species may be 

 found in the diagnosis as given by Busk : ' Cells in two layers, parted by 

 a calcareous septum.' In all the specimens figured in ' Crag Polyzoa ' ' 

 of Mesenteripora meandrina the transverse sections of the folia,ceous zoa- 

 rium are shown to have this septum very distinct. In many of Haime's 

 figures where cross sections are given, the septa are also shown to be 

 present. It seems to me, judging from the foliaceous specimens in my 

 own cabinet, that this ' calcareous septum ' is only an apparent, and not 

 a real character. If sections are made in a line with the cells, the only 

 axis visible is that made by sections of the cell-walls. In a cross section 

 of the foliations there is an apparent septal division, but the more closely 

 this is examined the less real will it be. The septal divisions of D. scohi- 

 nula, D. Terquemi, and D. cervicornis, as given by Haime, show one, two, 

 and three sections of cells on either side of the septal line ; and specimens 

 of Inferior Oolite species found in the neighbourhood of Cheltenham are 

 in many respects of a similar character. As I have been able to examine 

 only a very limited number of species, I should be glad to have more 

 detailed information if students of our Oolitic Polyzoa will address their 

 attention to this point. Meanwhile, by selecting the divisional name of 

 Milne-Edwards I shall not commit myself to any generic name dependent 

 upon a questionable structural character. 



Jules Haime, after very careful working, saw reason for establishing 

 fourteen species of biserial Diastopora, the whole of which are not found 

 in the same horizon in either this or other countries. Leaving D.foliacea 

 and X*. Lamourouxii we have nine foliaceous species as common to the 

 Jui'assic Fauna generally. Some of these range from the Inferior to the 

 Great Oolite and the Cornbrash ; whilst others, so far as observation at 

 present favours us, are confined to one horizon only. Two species given 

 by Haime — D. Michelini, Blainville, and D. Eudesana — ^range from the 

 Inferior Oolite through the Great Oolite ; and, according to Busk, is 

 possibly identical with the Mesenteripora meandrina found amongst the 

 Crag Polyzoa, and in recent Arctic fauna. I cannot assert positively that 

 the species are identical, or that we ought to accept all the synonyms of 

 Busk : still there is great probability in their favour ; but the fi-ag- 

 ments of Busk will bear no comparison in point of size with the fin& 



' riatos xvii. fig. 2 ; xviii. fig. 4 ; and xx. fig. 2, pp. 100, 1 10. 

 1882. S 



