164 REPORT—1883. 
Genus Ipmonga, Lamx. 
‘Zoarium erect and ramose, or (rarely) adnate; branches usually 
triangular. Zowcia tubular, disposed on the front of the branches, rang- 
ing in parallel, transverse, or oblique rows on each side of a mesial line.’ 
—Hincks, ‘ Brit. Mar. Polyzoa,’ p. 450. 
This ‘ world-wide’ genus is, so far as I am acquainted at present, 
very poorly represented in our British Cretaceous strata. Mr. Hincks 
(‘ Brit. Mar. Polyzoa,’ p. 451) says ‘many charming forms occur in the 
Cretaceous deposits,’ but these I have not seen. In the Chalk Marl of 
Charing we have a species very closely resembling Idmonea (Retepora) 
disticha, Goldf. It is only found in minute fragments, but it may be 
easily distinguished from the species of the next genus, by having the 
zocecia disposed on the front of the branches only. There are also traces 
of the delicate Idmonea Comptoniana, Mantell, but it is very rarely that 
specimens can be found even half the size of the specimen figured by 
Mantell. The author says: ‘This delicate Polyzoon (coral, Mant.) is 
dichotomons, cylindrical with elongated distinct cells, disposed in triplets 
at regular distinct intervals on one side of the stem.’! Mantell also figures 
and describes a species which he calls Idmonea Dizxonia, but I cannot 
identify the type. It ‘is found in the chalk of Kent and Sussex, often 
forming a cluster of branches two or three inches in circumference. The 
surface of the stems is covered with minute pores, and the cells are 
distinct and placed in single rows on the margin.’ It is very well 
illustrated in the ‘ Medals of Creation,’ Lign., figs. 6 and 12, p. 284. 
Many of the Idmonee(?) of the Cretaceous epoch described by 
D’Orbigny, Mr. Busk places doubtfully with Stomatopora as synonyms.” 
A mere casual reference to the synonyms of Idmonea atlantica, Forbes, 
will show how dangerous it would be to give specific names to the frag- 
ments described above. I have, however, given a list of British species 
described by Dixon and others. 
Idmonea Comptoni, Mantell. Up. Chalk, Chickester. 
a cretacea, Milne-Kd. > Sussex, Kent, Hamp- 
= I. Dixoni, Mantell (Morris). shire. 
- gradata, Defr. 
= Retepora disticha, Goldf. 
In Mr. Wiltshire’s paper on ‘ The Red Chalk of England’ (Geologist, 
1859, p. 275), a list of Cretaceous fossils is given, and one species of 
Polyzoa is identified as Idmonea dilatata, D’Orb.’ In the ‘ Catalogue of the 
School of Mines’ (Cretaceous), two species are given from the Up. Chalk: 
Idmonea cretacea, Milne-Ed., Up. Chalk. 
»  gradata? Defr. 
Hagenow describes no fewer than fifteen species of Ibmonea—breaking 
up Goldfuss’s Retepora clathrata and R. disticha, out of which he makes 
seven species; the rest are his own. One species—Letepora truncata, 
Goldf.—is taken with T. felix, Hag., as types of a new genus, Truncatula, 
Hagenow. 
1 Medals of Creation, p. 288; Lign. 64, fig. 14. 2 Crag Polyzoa, p. 113. 
® See also Brit. Mus. Catalogue, Pt. ili. (Busk), 1875, p. 15. 
