54 
dissepiments, whilst these, when present, arc always comparatively simple 
and few in number.” Dr. Clemens Schltiter has treated this subject at 
length , 1 and pointed out that sundry corals possessing dissepiments have 
been referred to Am plexus, c.g., A. lineatus, A. Ttoemer, A. ( Camp op hy llum) 
giganteus, Mich., &c., but as dissepiments are not present in the type species 
A . coralloicles, J. Shy., their absence may be accepted as a generic character, 
and the genus must he restricted accordingly; the late Prof. L. G. de 
Koninck denied 2 the presence of dissepiments in Amplexus. 
The tabulae of Amplexus proper are exceedingly well developed, 
complete, either horizontal or oblique, and usually distant from one another, 
or sub- vesicular, forming a wide, central, usually smooth area on which the 
septa do not impinge to any great extent, just as we find them in the various 
species of Tnjplasma. In other words, the latter, so far as its general 
structure is concerned, is an Amplexus in which the corallum is either 
simple or sub-fasciculate, the septal laminae spined, without a fossula, and 
reproduced almost wholly hy cilicular gemmation. Even in Amplexus, 
budding is believed, by some Authors , 3 to take place. 
The late Mr. James Thomson described 4 5 * the septa as either wanting, 
or delicate and short, and of one order ; a rudimentary fossula is also said to 
exist, “which is usually formed by a slight lateral depression of the tabulae.” 
All the species described by Thomson are simple, and are said to he “ developed 
from ova.” In two of the species, however, there are these peculiarities: — 
In A. Sowerbyi, Pliill., “ the septa are indicated by minute pointed granules,” 
and in A. irregularis, the secondary septa only are so. 
The community of structure between Acanthocles, Dybowski, and 
Tnjplasma has already been pointed out. 
Closely allied to Amplexus is Pycnostylus, Whiteaves . 0 The latter is 
said hy its describer to differ from the former “ only in the circumstance that 
it grows in colonies of compound and apparently fasciculate corallites. 11 It 
may also he said to differ, again according to Mr. Whiteaves, in its method 
of reproduction “ hy calicular gemmation at distant intervals into sets of 
three, four, or more ascending, subparallel, contiguous, flexuous branches.” 
1 Schliiter — Abhandl. Geol. Spscialkarte Preuss. Thuring. Staaten, 1889, VIII, Heft 4, p. 6 (264), f.n. 1. 
2 De Koninck — Nouv. Rech. Anim. Foss. Terr. Garb. Belgique, Pt. 1, 1872, p. 65. 
3 On this point see Schltiter — Abhandl. Geol. Specialkarte Preuss. Thuring. Staaten, 18S9, \ III, Heft 4, 
p. 8 (266). 
1 Thomson— Corals Garb. System Scotland, 1883, pp. 57-61. 
5 Whiteaves — Canadian Pal. Foss., 1884, III, Pt. 1, p. 3. 
r > Whiteaves— Canadian Pal. Foss , 1895, III, Pt. 2, p. 49. 
