Polyzoa Entoprocta and Ctenostoinata. 35 
4. The chitinous lining of the gizzard is usually rather thicker in H. cam- 
hodgiensis than in H. lacustris and the thin-walled oesophagus perhaps 
rather longer. 
5. In H. cambodgiensis the parietal muscles are, at any rate in the older 
zooecia, more powerful, consisting of more numerous and thicker 
muscle-fibres. 
JuUien's description of Norodonia was apparently based on dried specimens, in 
which the central part of the roof of the zooecia, especially if they be young, as a rule 
collapses, giving a somewhat false idea of the natural appearance. The ectocyst be- 
comes considerably thicker and darker in old zooecia than in young ones. 
The orifice in this species is as a rule rather small and the orificial tubercle very 
low. The former is in most cases surrounded by an incomplete circular or subcircu- 
lar horny ring, which is interrupted posteriorly. Occasional zooecia may be found in 
the older parts of colonies in which the ring is complete and subquadrate. More 
rarely it bears spines at its four corners, but one or more of the spines is usually 
abortive and I have not seen a case in which four well-developed spines were present. 
Zooecia developing in the depressions between ridges on the epidermis of Unionid 
shells are frequently assymmetrical, as in the branch figured on pi. i. 
The number and the arrangement of the parietal muscles are very variable, as is 
apparently the case in all species of the genus. The fibres seem to become stouter 
and more numerous as the ectocyst thickens with age. These muscles do not run 
parallel to the walls of the ectocyst as in Paludicella, Vidorella, Bowerhankia and 
other more or less tubular forms, but directly from the floor to the roof at some dis- 
tance from the sides of the zooecium, as in flattened forms such as Alcyonidium. In 
some cases they form a rather dense mass on either side of the polypide, but in young 
zooecia they are always very difficult to detect, 
Localities, etc. Jullien found the two forms here regarded as synonymous on 
Lamellibranch shells from an island in the Mekong River on the borders of Siam and 
Cambodia, from the interior of Cambodia and from the neighbourhood of Canton and 
the province of Ngan-Honi in China. My own examples of the species are on shells 
from the south-east corner of the Tai-Hu (Great Lake) in the Kiangsu Province of 
China. They were taken in the channel west of the island of Tong-Dong-Ding and in 
the Moo-Too creek, on a muddy bottom in from 6 to 10 feet of water, in December, 
1916. 
All specimens as yet found have been on the shells of molluscs ; my own were on 
those of Anodonta woodiana (Lea) the animals in which were alive. 
Hislopia malayensis, sp. nov. 
(PI. I, fig. 9; pi. II, figs. I, la.) 
The species may be distinguished by the following diagnostic characters. 
The colony is entirely adherent and of a more or less circular form, consisting of 
numerous primary branches that radiate from a common centre and give rise occa- 
sionally at an acute angle to lateral branches in the typical cruciform manner. 
