1848.] LONSDALE ON FOSSIL ZOOPHYTES. 7^ 



(fig. 5) next demand consideration ; but it is to the characters which 

 they exhibit in prepared sections (fig. 6) and mechanically-parted sur- 

 faces (fig. 7, 8) that attention must be chiefly confined. The struc- 

 ture was not noticed in the central area of one vertical slice (fig. G) ; 

 but in another (fig. G*), which displayed that portion of a branch to 

 a nmch greater extent, it formed a series of arched lines of unequal 

 curvature, and apparently continuous ; but in many instances the 

 layer did not extend across the abdominal cavity ; and where it did, 

 there was generally a slight cloudiness, as if a film of the wall or inter- 

 cellular structure had been included in the section : occasionally also 

 a transverse plate coincided in position with the curve. The greatest 

 distance between the centre of the arches never exceeded half a line, 

 and was often much less, while it gradually decreased as the lines 

 bent downwards and entered the outer zone. In that portion of the 

 coral, so far as could be ascertained (fig. 6), the concentric layers were 

 never far apart ; and this diiference between the middle and surround- 

 ing areas apparently depended on the cylindrical mode of growth, the 

 upward development far exceeding the transverse. It may be further 

 remarked, that in the axis of the coral, the digestive organs had little 

 to nourish except the periphery of the cavity and themselves, the 

 intermediate structure being very small ; whereas in the outer zone, 

 there was always a considerable amount of cellular composition ; and, 

 it is believed, that thi:; unequal demand necessarily allowed but a slow 

 increase of outward to upward extension. Vertical or transverse slices 

 afforded however no evidence of the actual nature of the concentric 

 layers, as they exhibited not a sign of a bilaminated composition. 

 Accidental cross-fractures gave sometimes a central boss (fig. 9), con- 

 sisting of a smooth, apparently solid network with open meshes ; the 

 former e\'idently representing one of the arches of the axis ; and the 

 latter proving that the concentric layer did not extend across the 

 abdominal cavities : moreover the sm^oothness showed, that the par- 

 tition had coincided with naturally separating surfaces. Minute 

 foramina not referable to young cavities were detectable in the sub- 

 stance of the network. Severed layers of the outer zone gave still 

 more satisfactory signs of composition ; and in one instance (fig. 7, 8) 

 the parted upper and lower laminae were preserved. First, as respects 

 the upper surface of the lower plate (fig. 7). The general surface 

 was more or less uneven, but smooth, or exhibited not the least trace 

 of having been structurally united to the upper lamina ; there were 

 also no projecting lines, like fractured edges of a reticulation. The 

 larger or abdominal openings were circular or oval, and had often a 

 raised margin ; while the smaller apertures, sometimes minute, had 

 likewise a tendency to a round outline, but the margins were de- 

 pressed : and between the openings a furrow was occasionally detect- 

 able, marking, it was believed, the boundary of the subjacent cell. 

 The under surface of the upper lamina (fig. 8) presented structural 

 counterparts to those just mentioned — the abdominal apertures being 

 generally sunk, and the margin of the minor frequently raised ; there 

 were also traces of projecting lines answering to the furrows in the 

 lower plate. These corresponding structures showed that the superior 



