62 Transactions of the Boyal Society of South Africa. 
probably of Cenomanian age. There are few species acknowledged 
to have so extensive a geological range as S. orbicularis. According 
to the latest views, as contained in Mr. H. Woods' memoir (Mon. 
Pal. Soc), it occurs in the Neocomian of Brmiswick (= P. Ger- 
manicm, Wollemann, Ahhandl. d. k. preussisch. Geol. Land. 1900 
(N.F.). pt. 31, pi. 8, figs. 13-19, p. 41), and is to be found in all the 
succeeding stages of the Cretaceous deposits right up to the Holaster 
suhglohosus zone of the Cenomanian series. It is easily seen, as 
pointed out by Mr. Woods, that some variations exist in this species, 
and that according to particular environment the valves may differ 
slightly in size, proportions, ornamentation, and even convexity. It 
is so with the Haldon examples, a large series of which are in the 
British Museum forming part of the William Vicary collection, and 
which Mr. Woods regards as a local variety under the name of 
P. orbicularis var. hcddonensis, because of the usually larger auricles, 
smaller apical angle, straight antero- and postero -dorsal margins, 
numerous ribs, and with a proportionally higher valve. It is to this 
group the specimen from Zululand belongs as after a strict com- 
parison, the details of structure are found to be in every respect the 
same as distinguishes the Haldon specimens. 
The species appears to be restricted to the British Isles and 
Central European localities, there being no records of its occurrence 
in either Africa or India. With regard to India, it may be mentioned 
that Stoliczka has described and figured two forms of Syncyclonema 
(obovatus and sivaicus) from the Utatur group of Southern India, 
which show the general features of S. orbicularis and are doubtless 
closely related, but without actual specimens for examination it is 
difficult to grasp their true affinities. The reference to Stoliczka in 
synonymy does not imply the existence of an Indian example — it is 
merely taken from a list of species in which Meek's genus Syn- 
cyclonema is apparently used for the first time in connection with 
this species. 
An Annelid-tube belonging to the genus Serpida (see p. 96) is in the 
same matrix with this specimen. It is about 30 mm. in length, of wide 
and gentle curvature, possessing a nearly uniform diameter (3 mm.), 
and ornamented with closely set annulations, the more elevated of 
which frequently enclose less prominent rings of quite microscopic 
size ; the tube is slightly bulbous in places, especially where the 
periodical constrictions occur. The transverse section exhibits a 
circular outline and a wall of about 1 mm. in thickness. This 
specimen shows certain resemblances to S. pinchiniana (Tate) var. 
ufiisinenensis of E. Etheridge from the Umsinene Eiver deposit (W. 
Anderson, "Third Eeport Geol. Surv. Natal and Zululand," 1907, pi. 1, 
