W. D. Lang—Cretaceous Polyzoa of the Family Idmoniide. 125 
II. Tue Suspivistons oF THE GENERA. 
In the following tables for the subdivision of the genera references. 
are given only to those forms which are figured ; for it is often almost 
impossible to be sure of the species intended by descriptions unaccom- 
panied by figures, in the case of these obscure forms. But as these 
tables are not intended to show natural relationships, but only as keys. 
to help the collector to determine the forms described in the British 
Museum Catalogue, the synonymy of the species is assumed to be that 
given in the Catalogue. ‘The remarks prefacing the table of the genus. 
Entalophora in the former paper are applicable here. The genera 
Crisina and Retecava are taken together, owing to the difficulty of 
separating them in practice. Theoretically a solid rod-like thickening 
occupies the reverse side of the zoarium in Retecava; while that of 
Crisina is not wider than the obverse side. But forms of Retecava 
occur, such as R. cypris (d’Orbigny) and &. grandis (d’Orbigny), in 
which the ‘ axial rod’ is reduced or hardly distinguishable ; while im 
Crisina ligeriensis, d’Orbigny, the reverse side is decidedly rod-like. 
The morphological significance of the ‘ axial rod’ stands or falls with 
that of the ‘canaux de renforcement’ of Pergens,! structures which 
can only be identified in longitudinal sections. 
IpMONEA. 
I. Zoarium of one or two (connected only at their proximal ends) strap-shaped. 
zocecium-bearing ridges, each of which may have its own ‘ selvage.’ 
A. Zoarium long and narrow (about six times as long as broad), with or without 
a ‘selyage.’ 
a. Zocecia emergent. 
Reptotubigera cristata, Meunier & Pergens, 1885, Nouv. Bry. 
Crét. Sup. : Mém. Soc. Roy. Malac. Belge, pl. ii, fig. 7. 
Idmonea cristata, Gregory, 1899: Brit. Mus. Cat. Cret. Bry., 
vol. i, pl. viii, figs. 4a, 40. 
b. Zocecia immersed. . 
Idmonea alipes, Gregory, 1899: Brit. Mus. Cat. Cret. Bry., vol. i, 
pl. vii, figs. 2. 3. 
B. Zoarium short (about three times as long as broad), rapidly becoming broader 
distally, without a ‘ selvage.’ 
JIdmonea virgula, V Orbigny, 1851: Bry. Crét., pl. 631, figs.15-17. 
Reptotubigera simplex, de Loriol, 1853: Invert. Mt. Saleve, 
pl. xvi, fic. 3. 
II. Zoarium of many zocecium-bearing ridges, rising from a common ‘selvage.’ 
A. Ridges short (seldom more than three times, generally about twice as long as 
broad) and straight. 
a. Two to three zocecia in a lateral series. 
Reptoclausa neocomiensis, de Loriol, 1863: Invert. Mt. Saleve, 
pl. xvii, fig. 7. 
b. Three or four zocecia in a lateral series. 
So ae obliqua, d’Orbigny, 1853: Bry. Crét., pl. 765, 
gs. 3, 4. 
c. Five or six zocecia in a lateral series. 
Reptoclausa neocomiensis, d’Orbigny, 1853: Bry. Crét., pl. 765, 
figs. 1, 2. 
1 Pergens, 1890, ‘‘ Revision des Bryozoaires du Crétacé,”? p. 311; and J. W. 
Gregory, 1899, Brit. Mus. Cat. Cret. Bry., vol. i, p. 149. 
