16 
VINE : CAMBEIDGE GEEEXSAND. 
Range of variation. — This is chief!}" noticable in the young, and 
in the older forms. In the young forms the striae are regularly 
disposed in longitudinal ridges, over and around the cells; in the 
older forms the striae become densely fenestrated, and the basal 
portion of the stem is covered with a thick coating of calcareous 
matter which entirely obscures the earlier cells. The disk-like base 
and the early portion of the stem of this species is most peculiar, and 
I have not the least doubt but that some of the forms of Osculipora 
plebeia — presently to be referred to — may be regarded as only the 
basal portion of the stem of E. striatopora. 
Locality : Cambridge, Greensand. 
6. — EXTALOPHORA NEOCOMIXENSIS, (?) D'Orb. Plate L, fig. 4. 
Entalophora id., D'Orb., Pal. Fr., p. 782, pi. G16, figs. 15-18. 
Spiropora pulchella, Rss. Foss. Anth. u. Bry. von Crosara, 
pi. XXXVL, figs. 4-5. 
Cricopora id., Rss. Poly. p. Wien., p. 40., pi. VI., fig. 10. 
Entalophora neocominensis, Waters, Quart. Jour. Geo. Soc, Vol. 
40, pp. 686-687. (Mr. Waters gives other synonyms.) 
There is a strange specific likeness in all the forms of this 
peculiar group of Fossil Polyzoa and I hesitated for a long time 
before placing the Greensand form here. It matters not whether 
we describe forms from the Lias, Jurassic, Cretaceous or Tertiary 
rocks, there is a possibility of confounding the various forms, if not 
carefully compared. In following Mr. Waters in his identifications, 
I do so on consideration of his placing the Spiropora pulchella 
Rss. in the group. This form I have carefully studied from speci- 
mens which were originally in Reuss's collection, and I can fully 
endorse the testimony of Mr. Waters as to the difficulty of separating 
the supposed synonymous forms. It must, however, be borne in mind 
that there are still difficulties in the way of fully accepting the whole 
of the synon^-my. In Spiropora, pulchella Rss. the cells are more 
closely packed in the branch than in the Greensand form — the orifices 
of the cells are smaller — and in some of the cells the lower lip of the 
peristome is very peculiar. Then again, Entalophora (Spiropora) 
pulchella Rss. is given by Novak, as a synonym of E. geinitzi Rss. 
on the other hand the puncturing of the cells in the Greensand form 
