69 
vermiformis, hut most so in T. wellingtonensis. On the other hand, there is 
hardly any distinction between the two orders in T. congregationis , whilst in 
T. princeps and T. columnaris the amount of disparity is variable. The two 
extremes in number to a cycle lie between T. vermiformis with twenty-eight, 
and T. delicatula with thirty-three, to T. columnaris , T. liliiformis, and T. 
princeps with eighty. As regards typical development, T. Lonsdalei presents 
the best example. 
The primary spines are longest in the species first mentioned and in 
r l\ wellingtonensis, in which they extend into the visceral chambers for at 
least one-third of the diameter of the latter ; they are long and tapering in 
T. columnaris, very short in T. congregationis and T. liliiformis , and 
delicate in the last species but one. The secondary spines are very short 
in T. vermiformis, and reduced to mere granules in T. wellingtonensis. 
The direction is, as a rule, obliquely upward, although in the last- 
named species and T. liliiformis horizontal spines have been detected, and in 
T. princeps there are some laterally curved. In T. Lonsdalei some of the 
spines are laterally denticulated, and in T. derrengullenensis there appear to be 
more cycles of secondary lamellae than primary in a given space, at any rate 
in the calice. 
Septal lamellae spined on the distal or free edges are by no 
means unknown in genera of Cyathophylloidea — for instance, in the 
Heliophyllidae they occur as transverse ridges or teeth, e.g., K. arachne, 
Hall . 1 Passing to the Zaplirentoidea we meet with the curious little 
Palceocyclus (if this genus is correctly referred to this order), in which the 
free edges of the lamellae are strongly echinulate. Moreover, in Heliophyllum 
and in some species of Thillipsastrcea the lamellae are provided with lateral 
carinae, i.e., oblique lamellar ridges directed inwards and upwards, which 
Nicholson compared ' 2 to the septal spines of Try plasma (Pholidophyllum) , 
and by analogy they may be equally compared to the lateral denticles on the 
spines in T. Lonsdalei. In all the corals mentioned there is this manifest 
difference — that whilst in them the lamellae extend to the centre of each 
corallite, and are therefore true septa, in the Tryplasmce they are simply 
peripheral. 
In contemplating the septal apparatus of Try plasma , it is impossible 
to divest one’s mind of the strong resemblance of the spines to those of some 
1 Hall— III. Dev. Fossils : Corals Up. Helderberg and Hamilton Groups, 1876, t. 24, f. 10. 
2 Nicholson— Man. Pal., 3rd Edit., 1889, I, p. 289. 
