63 
The mode of growth merely, 1 in one section of this genus, typified by 
T. Lonsclalei, recalls that of several well-known genera of Cyathophyllidae, 
snch as the fasciculate species of Lithostrotion, Diphyphyllum , Cylindro- 
phyllum, & c. The nature of the septal apparatus, however, absence of 
dissepimental tissue and septal loculi, or any form of peripheral tissue 
whatever, and the want of a fossula, will, on more attentive examination, at 
once distinguish the members of this section from these and their allies. 
2. Corallites. — In the sub-fasciculate species, and in T. vermiformis, 
the corallites are always long, generally slender, and cylindrical, straight or 
slightly flexuous, and gradually increasing in size upwards, round or oval. 
The greatest length yet measured of one of these corallites is six inches, the 
diameter varying from five to fifteen millimetres. The corallites of T. Lons- 
dalei var. minor are uniformly of the least diameter, five millimetres, those of 
T. Lonsdalei proper, the next in progression, from six to eight millimetres; 
those of the var. scalariformis six to ten, and even reaching to fifteen 
millimetres at points in their courses immediately preceding gemmiferous 
bifurcation, and imparting to such corallites a stronger and much more 
robust appearance ; the largest are those of T. congregationis, in which the 
normal diameter varies between ten and fifteen millimetres. The corallites 
are free during some portion of their course, and here and there united 
laterally by their Avails, or by cylindrical fistulse. In T. congregationis a larger 
proportion of the corallites appear to be united laterally than in the other 
species, and the fistulae are here developed to their greatest extent ; the 
corallites of this species arc also noticeable from a less regular longitudinal 
outline, frequently enlarging and contracting in diameter. 
Long cylindrical corallites are again met with in T. columnaris and 
T. dendroidea, and in both are either straight, Avitli a characteristically pipe- 
like appearance, or slightly flexuous for short distances. With the ultimate 
form of groAvth of T. columnaris AA r e are not acquainted, but in T. dendroidea 
budding probably brought about an open slirub-like corallum ; the former 
attains the largest diameter of any of the cylindrical species, from fifteen to 
twenty-five millimetres. 
In the folloAving species the early stage Avas simple, cylindro-ob-conical, 
or turbinate, retaining this form until the first gemmation took place. The 
cylindro-ob-conical type is seen in its fullest extent in T. princeps, which is 
also the largest species of this section of the genus. The large, stout corallites 
1 Omitting the fistu'se from consideration. 
E 
