THE EED CHALK OF HUNSTANTOT^. 475 



22. DiASTOPORA HUNSTANTONEN"sis, sp. nov. (Plate XIX. figs. 10 Cf, 



10 6.) 



Zoarium wholly adnate, forming a thin irregular discoid crnst 

 on a variety of fossils, without marginal lamina or stunted marginal 

 cells. Zocecia irregular hoth in breadth and length, but disposed in 

 series, and generally radiating from a central point ; robust and 

 strongly wrinkled or punctate on the surface. Central or nuclear 

 cells, short or stunted, consisting ordinarily of an " egg-cell " from 

 which other cells branch off in opposite directions; these are swollen 

 in the middle, slightly compressed towards the orifice ; orifice cir- 

 cular, raised ; peristome rather thick. Gomx'xmm either a double 

 or triple combination of cells or a sijigle large cell. Breadth of 

 ordinary colony from VJ. to 16 mm. 



Habitat. On Terebratula, Jnoceramvs, Ammonites, and almost on 

 every class of fossils previously referred to. Type on Terebratula 

 bijplicata. Fossils No. 1 (type) and 17 b ^. 



Horizon. Eed Chalk, Hunstanton. 



This is by far the most abundant and most prevailing form of all 

 the lied-Chalk Polyzoa. The larger fossils, especially the Ammo- 

 nites, have adherent to their exterior surfaces a number of colonial 

 growths ; while many of the smaller fossils, Inocerami especially, 

 have occasionally from one to three. The type form, however, 

 on Terebratula biplicata is one of the most beautiful examples of 

 the species. The double character on the surface of the zocecia, 

 wrinkled and punctate, is more noticeable on this than on the 

 other forms ; some of the cells being marked in regular transverse 

 dotted lines, while others are most irregular ; and on one edge of 

 the zoarium is an overlap of another colony, very strongly wrinkled, 

 bearing the peculiar r/onoscium, with its triple combination of cells, 

 referred to in the diagnosis. 



23. DiASToroE,A hun^staktoxensis, Vine ; var. A. (Plate XIX. figs. 



11 a, 11 6.) 



There are a few examples of this species, which, bearing most of 

 the characters of the typical form, differ sufficiently from them in 

 the disposal and markings on the surface of the cells to merit 

 varietal distinction. These varieties are not abundant on the Red- 

 Chalk fossils, but they have, nevertheless, well-marked characters. 

 Zoarium irregular, rarely discoid. Zooecia less wrinkled than in the 

 type, and more regular in their disposition or arrangement. Cen- 

 tral cells similar to those of the type-form. 



I have met with several forms of D. himstantonensis which, under 

 ordinary circumstances, would be justly regarded as varieties and, 

 in one case, as a new species ; but, being able to trace in most of 

 these particular features which seem to ally them to the type form, 

 or to var. A, I think it useless to load the text unnecessarily. 



Habitat. On Inoceramus and Terebratula. Fossils Xo. 17 c t, 

 ordinary variety, and No. 22, var. A. 



Horizon. lied Chalk, Hunstanton. 



