402 MK. A. W. WATEBS OlSr THE 



the Chilostomata ; but I do not think that there is any necessity 

 for dealing in detail with the conclusions that Mr. Longe drew ; 

 for doubtless he will now consider that it is made clear that the 

 structure of the movable horny operculum, and the calcareous 

 plate across the opening of tlie Cyclostomatous tube, is very dif- 

 ferent. I would also point out that there are, as far as I have 

 seen, differences of sliell structure which distinguish the Oolitic 

 Chilostomata and Cyclostomata ; and a number of characters 

 would enable the " race Diastoporidse " of Longe, containing 

 Diasto^ora, Tlntalopliora, ISscTiara, and Cellepora, to be readily 

 divided into their two suborders. 



It will be noticed in the Plate (figs. 5 & 6) that sometimes 

 instead of only one closure there are two quite close together. I 

 am not able to give any definite explanation of this ; but it must 

 be looked upon as having a very important bearing upon the 

 tabulae in Seteropora ; and Heteropora having been made the 

 basis of comparison with the Monticuliporcs and allied fossils, 

 these tabulse should be very carefully examined. 



Mr. Busk, in the ' Crag Polyzoa,' p. 122, speaks of partial 

 transverse nearly equidistant septa "* in Heteropora ; but unless 

 properly made sections have been prepared, there is a great chance 

 of being misled by appearances, and from fig^ 2 of pi. xix. I feel 

 no doubt whatever that there were no tabulse in the part of the 

 specimen figured by Mr. Busk, as I believe transparent sections 

 would have shown, whereas apparently only a broken surface 

 was examined. 



As pointed out f, I have made many sections of JSeteropora 

 without finding tabulae ; and as their presence indicates a stage of 

 growth or decay, they will not always be present. On the other 

 hand, I have now found closures in a number of cases, usually 

 only one in a zooecial tube ; but besides the closures near to 

 the circumference, there are sometimes others nearer to the 

 centre of the zoarium ; but in no case in recent, Tertiary, or 

 Cretaceous Heteroporidae have I found numerous tabulae, whereas 

 in what Haime calls Heteropora conifera I find the tabulae most 

 frequent, just as figured by Haime (' Bry. Jur.'pl. xi. fig. 2), and 

 they only average about 0*2 millim. apart. 



In Heteropora (IfuUicavea) lateralis, d'Orb., from Royan, I find 



* This term septa has been objected to by Prof. A. Nicholson ; and a protest 

 must also be made against the term opercula for these plates. 

 t " Note on the G-enus ffeterojwm," Ann. & Mag. Nat. Hist. vi. p. 156 (1880). 



