474 MR. G. R. VINE OX THE POLYZOA OF 



preserved on the fossil referred to, I canuot give further details, and 

 1 only place the species or variety as doubtfully present in the Red 

 Chalk. I have mislaid the fossil, but probably it ^ill be found, 

 marked " cast," in Mr, Jesson's Collection. 



Specialists working both on recent and fossil encrusting Polyzoa 

 have noticed that certain of the repent species apparently leave 

 behind them an impression on shell or stone, when all trace of 

 cell or cell-arrangement was destroyed. On fossil No. 23 is the 

 basal outline of a fine colony of Prohoscina, but of what species 

 I cannot say. The P. dilatata variety referred to was one of these, 

 and on the fossil referred to is another. 



Bahitat. On Terehratula hiplicata. Fossil No. 23. 



Horizon. Red Chalk (one "colony"). 



Genus Diastopora, Lamouroux. 



The genus Diastopora , as now accepted by authors, has had a 

 peculiar history. By Lamouroux, d'Orbigny, Haime, and others, 

 and even by M'Coy, the term Berenicea was used for adherent 

 discoid forms, and the term Diastojjora was reserved for foliaceous 

 forms. When, however, it was found that adherent Berenices 

 occasionally put on the habit of foliaceons species, the former term 

 was, to some extent at least, abandoned ; Vv'hile d'Orbigny in the 

 interval between lithographing the plntes of the ' Paleontologie 

 Fran(5-aise ' and writing the description of his figures, was evi- 

 dently undecided which term to use; for some of the figures in the 

 plates are named Diastopora, and in !he text the same figures are 

 described as Berenicea. Since the publication of ]:}usk's ' British 

 Museum Catalogue,' pt. iii., and Hincks's ' British Marine Polyzoa,' 

 the one term Dia^tojwra has been more frequently used ; but this 

 practice is by no means general ; even so lately as the new edition 

 of Phillips's 'Manual of Geology' in 1885, Mr. Etheridge still 

 clings to the old term. In the present paper, and in ray writings 

 generally, I make no distinction between the adherent and the 

 foliaceous forms. In the Red Chalk, however, there are none of 

 the latter ; but in the Jurassic rocks, both British and foreign, 

 the two groups are pretty evenly balanced. Mr. Hincks gives the 

 following as his definition of the genus : — 



" Zoarium adnate and crustaceous, or foliaceous, usually discoid 

 or flabellate, less commonly irregular in form. Zoa-cia tubular, 

 with an elliptical or subcircular orifice, crowded, longitudinally 

 arranged, in great part immersed " (' Brit. Mar. Polyzoa,' p. 457). 



The Diastojyoro' now to be described are peculiar. Most of them 

 are altogether unlike any known British Cretaceous forms; but 

 some of them are evidently allied to species, described by d'Orbigny 

 and others, derived from foreign Cenomanian or Senonian horizons ; 

 while others, such as D. hunstantonensis and its allies, are quite 

 distinct and new to science. 



