of Edinburgh, Session 1880 - 81 . 
225 
4. Minute structure of the corcdlum of Spring opora . — The 
minute structure of the corallum of Syringopora is best studied in 
thin transverse sections of the corallites. When examined in such 
sections, the wall of the tubes is seen to be composed of dense 
indistinctly fibrous or granular sclerenchyma (fig. 3, a), and to be 
Fig. 3. — A, Transverse section of a corallite of Syringopora reticulata, G-oldf., 
enlarged twelve times, showing the thick compact wall, the cut edges of 
the infundibuliform tabulae, and the septal spines, b, Part of the wall 
of the same section enlarged still further, showing the composition of the 
wall out of an outer light layer and an inner dark layer, and the origin 
of the septal spines from the outer layer, c, Longitudinal section of a 
corallite of the same, enlarged twelve times. The section passes obliquely 
through the corallite, and consequently shows different appearances in 
different parts of its course. At a it cuts through the inner layer of the 
wall, and exhibits the divided bases of the septal spines as rows of light- 
coloured spots (these are unfortunately left quite white, as if they were 
actually foramina, whereas they should properly have been faintly 
shaded); at b it cuts through the visceral chamber near its periphery, 
and shows the cut ends of the septal spines as rows of dark spots ; and 
below this point it becomes more nearly central, and shows the infundi- 
buliform tabulae. From the Carboniferous Limestone, Westmoreland. 
entirely devoid of any system of minute tubuli or canaliculi. The 
wall, in fact, is quite compact, and the visceral chambers of the 
polypes communicate with one another at no points except where 
the connecting-tubes of the colony may be developed. Very 
generally, the wall is distinctly composed of two layers, viz., the 
outer dense layer just spoken of and an internal layer of laminated 
