62 
IV -GENERAL STRUCTURE 1 2 OF AUSTRALIAN TRYPLASMJV 
1. Corallum or Colonies. — The species of our Tryplasmce present four 
types of growth. In three, T. Lonsdalei , audits varieties, T. congrega-lionis 
and T. clelicatula, the corallum is always in the form of fasciculate or sub- 
fasciculate masses of considerable size, the degree of contiguity of the 
corallites to one another varying considerably. In T. Lonsdalei, and its var. 
scalariformis the growth is loose and open, whilst in the var. minor it is 
compact. In well-grown colonies, particularly of the var. scalariformis, the 
corallites certainly radiate from one original point of growth. In T. con- 
gregations the colony is composed of closely arranged corallites, or separated 
from one another by moderate interspaces. 
The second group consists of T. columnar is and T. dendroidea. These 
possess a close external resemblance to some species of Amplexus, e.g., 
A. coralloides, J. Sby., in their long, columnar outline. The resemblance is 
intensified on transverse fracture by the appearance of the wide tabulate 
area of each corallite. 
The third section comprises T. princeps, T. liUiformis, and T. derren- 
gullenensis. The corallites of T. princeps, our largest solitary species, were, 
in their first stage, simple, ultimately forming gemmiferous bundles of 
considerable size. It is probable that T. liUiformis must be associated with 
T. princeps in its form of growth., for I have not seen any indication that 
the corallites commenced their existence other than as solitary individuals 
ultimately becoming bunches or aggregations by repeated budding, but of a 
looser formation than in T. princeps. 
The fourth and last section consists of one species, T. wellingtonensis 
in which the corallite, at first simple and solitary, by repeated single calicinal 
gemmation, gave rise to a chain of individuals, more or less retaining the 
habit of the parent corallite. 
1 Throughout Parts IV and V the following special terms need definition : — 
Radiciform processes. — Exothecal processes used as anchoring rootlets. 
Fistula’. — Exothecal hollow tubes uniting contiguous corallites. 
Bourrelets . — Circumferential swellings on the corallites, representing growth periods or the edges of old 
caliues. 
Costa . — Longitudinal exothecal ribs, or ridges, corresponding to primary septal lamellae. 
Rwjai . — Longitudinal exothecal ribs, or ridges, corresponding to secondary septal lamellae. 
Sej tal lamella. — Initial continuous laminae of the septal apparatus, extending from top to bottom of the 
corallites. 
Septal spines . — Denticles or spines forming the free inner or distal edges of the septal lamellae. 
2 Omitting from consideration that of T. (?) Murray! , 
