THE RED CHALK OF HUNSTANTON". 473 



form a peculiar group of Prohosclnce. The habits of the whole may 

 be characterized as follows : — Zoarium creeping, dendroid, with 

 narrow depressed branches, which nearly anastomose at the tips. 

 These branches are narrow at the base, enlarging towards the tops, 

 and bearing from two to six or seven rows of alternately disposed 

 cells. In his fig. 1, pi. 634, d'Orbigny figures a form of the natural 

 size, and enlarged in fig. 2. Taking this form, Prohoscina (Idmonea) 

 elegans, cited by d'Orbigny as P. Toucasiana, as above, the British 

 form which I place here resembles the habit of the more robust part 

 of the colony, where the branches anastomose. The zooecia, how- 

 ever, differ slightly. In a portion of the zoarium the cells are 

 arranged .similarly to fig. 4, pi. 634 ; but the surface is rather 

 rugose; in other portions of the zoarium the cells are depressed, 

 rugose, and stunted like the cells on the branches of P. fascicuJata, 

 d'Orb., fig. 11, pi. 634. On the whole, rather than make a new 

 name for the British form, I think it will be wise to leave this 

 unique example under d'Orbigny 's name, without any additional 

 varietal term. 



Habitat. On Terebratula hiplicata. Fossils Nos. 28 b and 19. 



Horizon. Red Chalk, Hunstanton ; Senonian Stage, d'Orbigny. 



20. Probosctn-a eamosa (?), d'Orb. 



1845. Diastopora ramosa, Michelin, Icon. Zoophyt. pi. 52. fig. 13. 



1847. Idmonea ramosa, d'Orb. Prodr. ii. p. 175. 



1852. Prohoscina ramosa, d'Orb. Terr. Cret. v. p. 851, pi. 632. 

 figs. 1-3, pi. 633. figs. 1-3. 



Mr. Hi neks (Brit. Mar. Polyz. p. 432) says " I do not venture to 

 identify Stomatopora expansa with d'Orbigny's Prohoscina ramosa, 

 though it bears a strong resemblance to it." There is certainly no 

 affinity between the present form, which I believe to be identical 

 with d'Orbigny's P. ramosa, and the recent Stomatopora expansa, 

 Hincks. Indeed the more closely that I study these Cretaceous 

 fossils, the less inclined I am to identify any of the species found 

 in the Ped Chalk especially with recent forms. 



In the list of references given above I have followed d'Orbigny,. 

 but the lied Chalk example now being described is more closely 

 allied to Idmonea cenomana of that author than to either Michelin 's 

 D. ramosa or Idmonea ramosa, d'Orb. ; but I believe that the whole 

 of the forms indicated are inseparable, the slight variation in the 

 habit being of little consequence. 



Habitat. On Inoceramns. Fossill^o. l-\c a. 



Horizon. Red Chalk, Hunstanton ; Prench horizon, Cenomanian, 

 Le Mans. 



21. Proboscina dilatata (?), d'Orb., var. cantabrigiensis (?), Yine. 



In my second paper on the Cambridge Greensand Polyzoa 

 (Bibliogr. 21) in describing the above variety (p. 261) I refer to an 

 impression of a species similar to, even if not identical with, the 

 Greensand form, on an Inoceramus. No zoarium nor zooecia bein.>' 



