F. D. Longe — Oolitic Polyzoa, 33 



Eace: DIASTOPORID^. 



Families or genera represented in the Oolites : 



Creeping : Diastopora ; 



Foliaceous : Bidiastopora ; Mesenteripora, etc. ; Elea ; Eschara. 



Dendroid: Cricopora; Melicertites ; Eiitalophora, etc. 

 Familes or genera repi-esented in the Chalk and subsequent periods : 



Creeping : Diastopora ; Lepralia, etc. ; C'ellepora, etc> 



Foliaceous : Mesenteripora ; Eschara, etc. 



Dendroid : Entalophora ; Myriozoum ; Vincularia, etc. 



EXPLANATION OF PLATE II. 



Figures 1 to 6 are taken from Oolitic forms. They represent small portions of 

 surface, about 2 x 1|- mills., magnified about 20 diameters. 



Fig. 1 belongs to an Escharoid form having a similar growth to that of the living 

 Eschara foliacea, Lamk. Busk, etc. It developes large lamellae of an irregular 

 rectangular shape, which anastomosing together at right angles form hollow- 

 chambered masses of upwards of a foot in dimension. The cell texture is essen- 

 tially that of Diastopora. Some of the cells are decumbent, and confined within 

 the general surface of the lamellae. Others have their oval extremities protruding 

 and tubular. The orifices of the decumbent cells are generally round with thick 

 rims or peristomes. The specimen figured has retained too little of the original 

 sui'faee to afford much evidence of opercula. 



This species would probably be classed by D'Orbigny as a Bidiastopora. It is 

 very like D. Lamourouxi of Haime. The type is common in the Pea-grit of 

 Cleeve Hill. 



Fig. 2 is also an Inferior Oolite form from Cleeve Hill. I have identified it with 

 a specimen in the Cambridge Museum, named by Haime B. Wrighti. The 

 specimen figured is in good preservation, retaining its white calcareous surface, and 

 showing the characteristic punctation of the Biastoporidce in the coenoecium, and 

 in the lids which appear in several of the cells. It differs from Fig. 1 in having 

 the cells more regularly arranged, and more evenly laid on the lamellae. The 

 orifices are rimmed like those of the decumbent cells in Fig. \. In parts the cells 

 show a slight tendency towards protrusion. The cell margins, formed by the 

 coalescence of adjoining tubes, are seldom very prominent ; but they appear very 

 distinctly in parts where the surface has been abraded, and the similarity of the 

 structure and arrangement of the cells to that of the living Eschara foliacea, 

 Fig. 7 is very apparent. This form would probably be classed as an JSlea by 

 D'Orbigny, and as Mesenteripora by Blainville and Busk. 



Fig. 3 is also an Inferior Oolite form. The ceils are all decumbent and much 

 depressed, margins very prominent in parts. The orifices are sunk or thin rimmed. 

 In several of the cells they are clearly sub -terminal, as in the typical Cheilostomatous 

 cell. In this specimen the original punctui-ed siurface is well retained, both in 

 the lids closing the orifices, and in the smToimding coenoecium. This form shows a 

 further advance towards the Cheilostomatous type, the tubular shape of the cells 

 exhibited in Figs. 1 and 2 being much less maintained. 



This form is very like B. Mettensis of Haime. It would probably be classed as 

 an Mea by D'Orbigny. 



Fig. 4 is from the Forest-marble beds at Luc near Caen in Normandy. These are 

 the same beds as those of Eanville, from which so many of the best specimens 

 of the Oolitic Polyzoa have been obtained. 



In this form the modification of the tubular cell is carried still further. 

 Longitudinal compression, producing a lateral bulge, has transformed the tubular 

 into the oval shape, while the regularity ^\'ith which the cells are arranged, and 

 the prominence of their margins, produces i\\e symmetrical areolation which is so 

 characteristic of the Cheilostomatous Escharoids. The orifices are round and 

 rimmed. The symmetrical character represented in the figure is only confined to 

 parts of the coenoecium. In other parts the shape and arrangement of the cells is 

 sufficiently irregular to show its affinity to Biastopora, 



DECADE II. — VOL. YIII. — NO. I. 3 



