42 
II.— HISTORY OF THE GENUS TRY FL ASM A. 
Tiie history of Tryplasma is a peculiar one and must ho studied in detail to 
ensure a proper understanding of the following remarks : — - 
1845.— W e owe the name to Mr. W. Lonsdale, 1 who employed it for a 
coral from the Silurian rocks of the Ural Mountains, and regarded it as a sub- 
genus of Cyathophyllum. The only species described was T. cequabilis, 2 but in 
a foot-note to his description the author included also Cyathophyllum artic- 
ulatum , Wahl., or a coral he took to be this form. In the explanation of his 
plate he wrote as follows: — -“The coral, believed to be the Cyathophyllum 
articulatum of M. Ilisingcr, is given to prove that the peculiar characters 
exhibited by Tryplasma cequabilis occur in another coral with a sufficient 
amount of a differential structure to warrant the establishing of a second 
species, and, therefore, the proposing of the sub-genus. 3 
The type, T. cequabilis, is a cylindrical, solitary coral, with a thin outer 
wall, a broad central, tabulate area, an outer narrow septal zone, the septal 
lamellae numerous, alternately larger and smaller, and round “ foramina ” ; 
the tabulae were conceived to be continuous through the septal lamellae to the 
outer wall. This is practically Lonsdale’s definition, although not exactly in 
his words. The figure 4 * of the supposed C. articulatum displays a similar 
structure to that of T. cequabilis, and in addition, being a compound form, 
the corallites united by connecting bars [fistulae], rendering the corallum 
more or less fasciculate. 
A thorough conception of the meaning of Lonsdale’s “foramina” is 
essential to a true understanding of the structure of Tryplasma. He said: 
“ The peculiarities consist, — first, in the lamellae [septal lamellae] 6 of the outer 
area being pierced, from the inner surface of the Avail, through their Avhole 
breadth by well defined relatively larger foramina, terminating on the inner 
edge [free inner border of the septal lamellae] in a distinct row of short 
tubuli ; and, secondly, in the total absence of interstitial vesicular laminae 
1 Lonsdale — Murchison’s Geol. Russia in Europe, 1S15, I, p. 613, 
2 Lonsdale — Loc. cit., t. A, f. 7, la. 
3 Lonsdale — Loc. cit., p. 633. 
1 Lonsdale — Loc. cit., t. A, f. 8, 8ra. 
* The words within square brackets are mine, 
