vine: fossil polyzoa : additions to the cretaceous lists. 155 
Zoarium simple and uniserial. Zooecia elongate, sub-ovate pro- 
duced or attenuated below ; area oval or circular, occupying nearly 
the whole front of the cell ; area walls smooth or slightly crenulated 
when aged ; the produced portion of the wall below the area folded 
or puckered (see fig. 15). Zooecia generally linked together in linear 
series, branching laterally sometimes from every cell, but in the 
figured example ^fig. 15, pi. VI.) the mode of branching is most 
peculiar, this however is an exceptional feature. The lengths of the 
cells, including the attenuated portions, vary considerably, but 
generally speaking the measurement is from about one-tenth to one- 
sixteenth of an inch in length. 
Locality and Horizon : Gault in situ, Barnwell, Cambridge. The 
forms described from the Red Chalk of Hunstanton, are destitute of 
the "puckering" of the cell wall just below the area. 
Since I wrote the description of this species, as published in my 
" Red Chalk Paper " (Quart. Journ. Geol. Soc, vol. 46, p. 484), I have 
examined many allied forms derived from the British Upper Chalk of 
Chatham, Salisbury, and also from Norfolk ; and as these forms have 
been characterised by Marsson (Hippothoa dispersa = Cellepora 
dispersa, Hagenow, 1839), it may be well to keep the Upper 
Chalk forms distinct. 
IV. Membranipora fragilis, d Orb. Var ? 
1851. Flustrellaria fragilis, d'Orb. Terr. Cret. p. 515, pi. 723, 
figs. 3-9. 
Zoarium very irregular. Zooecia irregularly disposed, sometimes 
in linear series with two or three rows of contiguous cells, but more 
frequently in single series, but these continually twist and twirl in a 
variety of ways, which for the purposes of description are most con- 
fusing ; the disposition and habits of the cells generally may be 
described as oval, with large area occupying nearly the whole of the 
front. The cells of this species are more closely allied to the 
Flustrellaria fragilis, d'Orb. (1. c, pi. 723, figs. 6 and 8) than to any 
other species known to me. The Zoarium of the British example is 
more than half an inch in width and breadth, and from some portions 
it would be quite possible to construct a drawing similar, ovicell and 
all, to that of d'Orbigny's figures (6 and 8, pi. 723). 
