53 
III.— DELATION TO OTHER GENERA, AND SYSTEMATIC 
POSITION OF TRYPLASMA. 
The family Palmocyclidae, instituted by Dybowski , 1 contains several genera 
of small, simple, discoidal or bowl-shaped corals, some of which, at least, 
possess lamellar septa crenulated on their free edges and granulated laterally 
— such, for instance, are Palceocyclus, Ed. and II ., 2 and Acanthocyclus, 
Dybowski . 3 
Palceocyclus, according to the late Prof. P. M. Duncan , 4 5 possesses 
tabulae, a fossula, and endotliecal tissue [septal dissepiments]. In the presence 
of the two latter structures it therefore differs from Tryplasma. On the 
other hand, the late Prof. Iv. Z it tel' says that throughout the family both 
tabulae and dissepiments are wanting. Acanthocyclus 6 is described by 
Dybowski in but very few words, and really does not appear to possess any 
characters of importance separating it from Palceocyclus. 
The presence of tabulae, septal spines, radiciform processes or 
anchoring rootlets, and fistulae at once distinguishes Tryplasma from the 
simple corallum of Petraia, Munster, as restricted by E. Roemer 7 8 ; indeed, 
the septal structures are but very feebly developed at all in this genus. 
Erom all the Amplexus- like forms, Tryplasma is separated by the 
presence in the latter of septal spines, although in some other points there 
is a close degree of resemblance. In Amplexus the corallites are always 
simple and solitary, s and occasionally hollow radiciform processes are developed. 
The septal lamellae are remarkably rudimentary, narrow as in Tryplasma, but 
unlike those of the latter, these lamellae, in all typical Amplexi, are never 
produced into spines on their inner or free edges ; a septal fossula is present, 
hut never in Tryplasma, and dissepiments exist in neither. Messrs. J. 
Thomson and II. A. Nicholson say 9 “there mayor may not be interseptal 
1 Dybowski — Zoantharia Scler. Rngosa, Pt. I, 1873, p. 77. 
2 H. Milne-Ed wards and Haime — Archiv. Mus. Hist. Nat. Paris, 1852, V, p. 203. 
s Dybowski — Zoantharia Scler. Rugosa, Pt. I, 1873, pp. 77 and 103. 
4 Duncan— Phil. Trans., CLVII, p. 651. 
5 Zittel — Text Book Pal. (Eastman’s Edit.), 1900, I, p. 74. 
G Dybowski — Zoantharia Scler. Rugosa, Pt. I, 1873, p. 103. 
7 F. Roemer — Lethsea Pal., 1883, I, Lief. 2, p. 410. 
8 H. Milne-Edwarus and Haime — Archiv. Mus. Hist. Nat., 1852, V, p. 325 ; Thomson and Nicholson — 
Ann. Mag. Nat. Hist., 1875, XVI (4j, p. 424; Schliiter— Abhandl. Geol. Specialkarte Preuss. Thuring. Staaten, 
1889, VIII, Heft 4, p. 8 (266). 
9 Thomson and Nicholson — Ann. Mag. Nat. Hist., 1875, XVI (4), p. 425. 
