THE RED CHALK OF HUNSTANTON. 483 



pp. 589, 590) he cites Zonopora (probably Z. undata) as occurring 

 in Cenomanian strata ; and five species of MicUicrescis, three from 

 the Neocomian, but the other two are not located ; and also one 

 species of Ceriocava from the Gault. 



Genus Unicatea, d'Orb. 



1826. Melobesia, Aud. (non Lamouroux) ; 1839. Tiihulipora 

 (pars), d'Orb. ; 18-18. Defraacia^ lieuss (non Bronn) ; 1852. Uiii- 

 cavea, d'Orb. Terr. Cret. v. p. 970. 



The genus Ujiicavea, as fonnded by d'Orbigny, embraces a most 

 peculiar group of fossils (Lichenojjoridce, Hiucks). The colony is a 

 very simple, discoid, dome-like zoarium, fixed by the whole of its 

 imder surface to some foreign body, sometimes surrounded by a 

 basal lamina, which is not always apparent in some of the species 

 of the genus. The zooecia are disposed in primary and intermediary 

 rays, each of which bears the orifices of depressed tubular cells. 

 Between the rays are cancellated interspaces, with a depressed, 

 cancellated, non-zocecial space in the centre of the zoarium. Uni- 

 cavea radiata (Audouin), one of d'Orbigny's species, is cited by Busk 

 as Biscoporella (Catal. Mar. Polyz., Cyclostom. Polyz. 1875, p. 32), 

 and by Hincks as a Licheiiopora (Brit. Mar. Polyz. p. 476); but 

 as none of the figures compare favourably with the lled-Chalk forms, 

 w^hich I shall place in the genus Uniaavea, I make no apology for 

 passing over the recent species, ignoring at the same time some 

 citations by d'Orbiguy and others. 



38. Unicayea collis, d'Orb. 



1850. Actinopora collis, d'Orb. Terr. Cret. v. pi. 643. figs. 1-4. 



1852. Uiiicavea collis, d'Orb. ibid. p. 973, pi. 778. figs. 1, 2. 



There are a few forms in the Eed Chalk that may be regarded 

 as allies of the French Senonian species, even if they be not iden- 

 tical. The zoaria are dome-like and fully attached by the under 

 side to foreign bodies. The zooecia are disposed in primary and 

 intermediary rings, which begin to form a little beyond the central 

 cancellated centre. The examples are too badly preserved to allow 

 me to discuss the Lichenoporidal features, ovicells or cancellse, 

 entered into by Mr. "Waters * ; but the characters, so far as 1 can 

 make out, are more in accord with the Cretaceous (Senonian) forms 

 than with any recent example of Lichenopont radiata, And., known 

 to me. 



Uiiicavea collis, d'Orb., must not be confounded with Reptomultl- 

 cava collis, d'Orb., already described. The species are quite 

 distinct. 



Habitat. On Terehratula, Inoceramus, and Bourgueticrinus. Fossils 

 Nos. 37, var. A, on Terehratula ; 38, var. B, on Bourgueticrinus. 



* A. W. Waters, 1884, pp. 694-5, Quart, Journ. Geol. See. vol. xl. ; 1887, 

 pp. 345-347, vol. xliii. ; "On the Ovicells of soiue Lichenoporidae," Journ. 

 Linn. Soc, Zoology, vol. xx. pp. 280-285 (1888). 



