96 
OSCCLIPORID^. 
D. 3969. 
B. 4207. 
B. 4483. 
B. 4484. 
B. 7134. 
B. 7279. 
B. 7280. 
60,343. 
A young zoarium showing both faces. Middle Chalk — zone of 
Micraster cortestudinarium. Chatham. Gamble Coll. 
A young zoarium showing both faces. Middle Chalk — zone of 
Micraster cortestudinarium. Chatham. Gamble Coll. 
A branched fragment. Upper Chalk. South-east of England. 
Toulmin Smith Coll. 
A long branch and two isolated fragments. Chalk. Loc. ? Old Coll. 
A fragment of a large zoarium showing the obverse surface, and part 
of a young zoarium showing the carinate reverse face. Chalk. 
Caterham, Surrey. W. Ogle Coll. 
Four fragments of zoaria. Chalk. Beachy Head. Presented by 
Dr. J. W. Gregory, 1899. 
Four fragmentary zoaria. Chalk. Loc. ? Toulmin Smith Coll. 
A zoarium with crowded branches and long pinnules, with very 
prominent reverse ribs, and three isolated fragments of the same. 
Upper Chalk — zone of Micraster coranguinum. Gravesend. 
Dixon Coll. 
Foreign. 
B. 3733. A fragment of Supercytis digitata with gonoecium (on slide). 
Senonian. L’ Arche de Leves. Identified by M. Pergens. Gamble 
Coll. Purchased. 
UI^HEPRESE^^TED SPECIES. 
1. alternatus (d’Orbigny), 18.54. 
Syn. Truncatula alternata, d’Orbigny, 1854. Bry. Cret. p. 1057, pi. 797, 
figs. 1-4. 
,, ,, Bucaille, 1890. Bry. Cret. Seine-Inf. : Bull. Soc. 
Sci. nat. Kouen, vol. xxv. p. 508. 
,, ,, Pergens, 1890. Rev. p. 385. 
non Homceosolen alternatus, Vine, 1893. Compl. Rep. : Rep. Brit. Assoc. 
1892, p. 334. 
Char. — Zoarium tufted, with long dichotomous branches, which appear strongly 
bi-serrate owing to the short, crowded, alternate, lateral processes, which are 
strongly reflexed, and they are marked on the reverse side by longitudinal ribs. 
Zooecia crowded ; the interzooecial spaces are few and small. There are from 
ten to twelve zooecia in the width of the branch, and the lateral apertures may 
be serial or subserial. 
Distrib. — Turonian : Martigues, Bouches-du-Rhone ; Angouleme, Charente ; 
Seine -Inferieure. 
Aff. — T his Turonian form closely resembles the Senonian Bryozoa for which 
d’Orbigny founded his species Truncatula gracilis. They may be only varieties 
of the same species ; they both agree in having crowded, overlapping, alternate 
processes, which bend backward from the plane of the axis of the branch, and 
have well-marked longitudinal fluting on the reverse face. The T. gracilis of 
d’Orbigny, a synonym of Homocosolen striatus (Hag.), has longer and more 
slender branches, with the processes more distant than in H. alternatus. 
