CORALS OF THE LONDON CLAY. 41 



Order 2.— ALCYONAEIA. 

 Family PENNATULID^E. 



Genus Graphularia. 



Graphtjlaria Wetherelli. Tab. VII, figs. 4, 4 a, 4 b, 4 c, 4 d, 4 e. 



Pennatula, J. Decarle Soiverby and Wetherell, in Geol. Trans., 2d series, vol. v, part 1, 

 p. 136, tab. viii, fig. 2 a, b, 1834. 



Corallum styliform, straight, very long, cylindroid towards the lower extremity, sub- 

 tetrahedral at the upper part, and presenting on one side a broad shallow furrow. Surface 

 appearing smooth, when examined by the naked eye, but showing, when placed under the 

 microscope, a multitude of small, longitudinal, closely-set, striae, that seem to indicate a 

 fibrous structure. Transverse section showing the existence of a thin coating and a 

 radiate structure in the body of the Coral. Diameter of the thickest part, two thirds of a 

 line ; probable length, more than a foot. 



We have only seen small fragments of this styliform Coral, that evidently constituted 

 the central stem of some aggregate polypi of the family of the Pennatulidae. Some of 

 these broken remains are almost cylindrical, and usually thicker than others that are 

 imbedded in the same mass of clay, and have a sub-tetrahedral form ; others, again, are 

 intermediate between the former, both by their size and their form, and have the same 

 radiate structure and striated surface. It is therefore probable that they all belonged to 

 the same species, and constituted a long, slender, sclerenchymatous axis, somewhat similar 

 in form to that of Pennatula, but resembling that of Virgularia by its structure. The 

 characters of the corallum thus reconstructed are also nearly allied to those of Pavonaria 

 and Umbeliularia, but differ from those of all the known recent genera of Pennatulidae. 

 It is brittle, and presents a radiate section, as in Virgularia, but is not cylindrical from one 

 end to the other, as is the case in the latter, nor is it from top to bottom of a tetrahedral 

 form, as in Pavonaria ; it never appears to be twisted like the stem of Umbeliularia ; it 

 united in its different parts the two forms that are found separately in the two first- 

 mentioned genera, and so far resembles Pennatula ; but in the latter the square portion is 

 situated towards the lower end, and the apex is cylindrical, whereas in the above-described 

 fossil, it is the upper slender part that presents a square section, and the thick basal part is 

 cylindrical ; it must also be remembered that the axis of Pennatula is not very brittle, and 

 does not present a radiate structure when cut transversely, but appears rather of a fibrous 

 structure. In the recent genus Lithuaria, the styliform axis is tapering towards the lower 

 end, and inflated, pitted, and even somewhat echinulate at its upper extremity. It is also 

 impossible to refer the elongate stem of our London Clay Pennatulida to the genus 



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