192 
EETECAYA. 
zooecia appear to occur singly and alteraately. Older fragments 
of the Sussex fonn have, however, no trace of a median lino, 
and lateral examination of the branches shows that the apertures 
are triserial. As is so often the case with Dixon’s Collection, the 
exact locality whence his specimens came is unknown. 
LIST OF SPECIMEXS. 
British. 
D. 2955. Nine fragments of a zoarinm from the Chalk of Sussex, including 
those figured by Lonsdale: Dixon, Geol. Sussex, pi. xviii. a, 
figs, oa, b, c, d, e,f, and g. Dixon Coll. Three of the fragments 
are refigured as PI. IX. Figs. 8a, b, and c. 
D. 4491. Zoarinm showing reverse face and isolated fragment of the same (in 
tube). The latter shows spine on reverse surface. Upper Chalk. 
Loc ? Dixon Coll. 
D. 2838. Two fragments (on slide). Upper Chalk. Bromley. J. Simmons 
Coll. 
D. 3110. A large zoarinm with a fragment on slide, and a second fragment 
showing gonoecium. Fragment (on slide). Upper Chalk. North- 
fleet. Wetherell Coll. 
D. 3127. Fragment with high peristomes (on slide). Upper Chalk. Kent. 
Simmons Coll. 
Foreign. 
D. 8749. Two fragments (on slide). Senonian. L’ Arche de Leves. Gamble 
CoD. 
3. Retecava ramosa (d’Orhigny), 1850. 
Stxoxymy. 
Crisina ramosa, d’Orhigny, 1850. Prod. Pal. vol. ii. p. 266. 
,, ,, d’Orbigny, 1851. Bry. Cret. pi. 611, figs. 11-15. 
Idmonea ,, d’Orbigny, 1853. Bry. Cret. p. 736. 
,, ,, Pergens, 1890. Eevision, pp. 312, 347. 
Idmonea macilenta, von Hagenow, 1851. Bry. Maastr. Kr. p. 29, pi. ii. fig. 4. 
,, ,, Hamm, 1881. Bry. mastr. Ob. -Sen. p. 31. 
„ ,, Ubaghs, 1888. Compt. Rend. Exc. : Bull. Soc. beige Geol. 
vol. i., Mem. p. 233. 
,, divaricata, Ubaghs, 1865. Bry. Schicht. Maast. : Verb, naturh. 
Ter. Preuss. Rheinl. vol. xxii. p. 58, pi. iii. fig. 8. 
,, ,, Staring, 1860. Bod. Nederl. vol. ii. p. 400. 
Diagnosis. 
Zoarium of laterally compressed dichotomous branches, which 
remain free laterally or unite to a network. The reverse side 
of the branches is occupied by a strong axis, which is broader 
