50 
PEOBOSCIXA. 
characters of the zooecia are Tubuliporidan, not Idraoniiform. 
The specimen illustrated by Fig. 1 illustrates the accidental 
character of the linear series of peristomes in this species. One 
branch of the zoarium has the peristomes in regular transverse 
series, situated further apart than in the typical form of radio- 
litorum, and approaching the condition of * Beptotuhigera marginata' 
Fig. I . — Prohoscxna radiolit rum (Orb.) ; two branches of the same zoarium, one 
with irregular and one with regular transverse series of apertures. Middle 
Chalk : Chatham. Vine Coll. D. 975. 
Orb.^ In the adjacent branch the zooecia are quite irregular in 
arrangement. 
A specimen of P. cornucopice (So. D. 485) also shows a local 
adoption of a linear arrangement of the peristomes. 
The Jurassic representative of this species is F. eudesi, Haime,* 
which has smaller apertures and a flatter zoarium. 
LIST OF SPECIMENS. 
British. 
D. 300. On fragment of Inoceratnui. Upper Chalk. Gravesend ? Presented 
by F. Harford, Esq. Figd. PI. III. Fig. 5. The typical form 
of this species. 
D. 3857. Encrusting a fragment of Mkraster^ sp. (on shde). Middle Chalk. 
Chatham. Gamble CoU. 
1 D’Orbigny : Bry. Cret. p. 753, pi. 750, figs. 19-21. 
- Haime. Mon. Bry. Jur. : Mem. Soc. geol. France, ser. 2, vol. v. p. 167, 
pi. T. figs. 9o, b. 
