68 
11. Septal Lamellce and Spines. — We may now consider the most 
important feature of this group of corals — the structure of the sejital apparatus. 
This consists primarily of narrow longitudinal lamella}, extending from top 
to bottom of every corallite, and which spring from the theca as in other 
sclerodermic corals ; and secondly, the distal or inward edges of these lamella} 
are broken up into spines of greater or less length, hut never attaining any 
great degree of length ; the septal apparatus may, therefore, he described 
generally as marginal or peripheral. This feature is common to and constant 
throughout the whole group, varying only in degree specifically. There is a 
decided, although at times slight, difference in length of these spines in 
alternate rows, indicating the presence of primary and secondary lamellae, the 
secondary spines being occasionally reduced to mere granules on the free 
edges of the lamellae. The spines, thorn-like projections, invariably point 
upwards obliquely in the direction of growth of the coral, and form a good 
index for determining the upper and lower surfaces of a colony when this is 
not otherwise apparent ; horizontal spines are here and there present also, as 
well as laterally curved, but these cannot be regarded as other than occasional. 
The number of cycles in an intertabular space does not appear to follow any 
constant rule, these cycles varying from one to four, and in some cases more. 
In T. ( Acanthodes ) tubulum, Dyb., and T. ( Acanthodes ) rhizophorus, T)yb., 
four cycles occur, but in T. ( Acanthodes ) cylindrica, Dyb., there appears to 
be only one. 
The septal spines are neither tubular nor hollow, although so described 
by Lonsdale and Dvbowski. Yon Koch says that the central line [primordial 
septum] in each is dark coloured in T. (Pholidophyllum) Loveni, Ed. and II., 1 
and this is frequently to be seen in sections of our species. 
In transverse sections prepared for the microscope, the septal spines 
often appear much broken up, and dot like — this is due to the section 
cutting the upwardly projecting spines of more than one cycle. Similarly, 
when a longitudinal section is cut eccentrically and close to some portion of 
the corallite wall, the same cut ends again appear as so many vertical lines 
of disconnected dots. 
The lamella} in T. Lonsdalei and T. princeps are very narrow, and 
purely marginal in T. welling tonensis and T. liliiformis ; they are stout and 
strong in T. princeps, but very delicate in T. congregationis. The separation 
into primary and secondary is distinctly marked in T. Lonsdalei and T. 
1 Weissermel — Zeitsch. Dents. Geol. Gesellsch., 1894, XLVI, Heft 3, p. 640. 
