Mr. W. Lonsdale on the Genus Lithostrotion. 455 



lype" {op. cit. p. 603). Martin's specimen was silicified (Pet. 

 Derb. /, c), apparently a prevalent mode of mineralization, and 

 less favourable to the exhibition of minor stnictures than when 

 the process has been effected by carbonate of lime; but his 

 figures 3 and 4 (tab. 43) clearly express a triple composition ; 

 and many terminal cavities of the specimens examined displayed 

 no greater amount of detailed composition than is given in those 

 delineations, while others in the same mass exhibited fully the 

 peculiarities of each area. The mode of reproduction is neither 

 represented nor mentioned by Martin ; but in a large, siliceous 

 Derbyshire specimen of very irregular growth, obligingly lent to 

 the author by Mr. Wilson of Lydstip House near Tenby, in- 

 stances were detected of what appeared to be young germs deve- 

 loped within the area of the parent column ; also of others based 

 upon the united edges of two closely applied mature termina- 

 tions ; and they plainly could not therefore have sprung either 

 from the side of the old corallites or from an interspace ; while 

 some could not be assigned to a definite position with respect to 

 pre-existing stems. It is obvious, that where the gi-owth was very 

 irregular, and the vesicular or outer zone was squeezed into a 

 vertical position or greatly compressed, germs and young columns 

 may appear to occupy anomalous situations ; and the difficulty 

 in forming a right inference is increased when transverse sec- 

 tions cannot be consulted. Among the staple productions of the 

 Clifton or Bristol dealers is however one, which possesses all the 

 essential structures of the Derbyshire coral. It is apparently 

 included by Mr. Phillips ^= under the designation Cyathophyllum 

 crenulare ; which is regarded as different from Cyath. floriforme, 

 the term applied to INIartin's fossil ; but the distinction is only 

 specific ; and it remains to be ascertained, if under equally favour- 

 able opportunities for examination, any real variations exist. 

 The Clifton specimens being calcareous are easily cut ; and 

 transverse sections containing illustrative examples of the mode 

 of producing young corallites may usually be obtained. In an 

 early state, the germ, situated in the vesicular zone and in 

 general partly in contact with the wall of the parent, presents 

 a small, round, oval or irregular area, defined by an opake 

 white uneven line ; and according to the degree of advancement, 

 rudimentary lamellae, everywhere equally imperfect, issue from 

 the boundary : an incipient axis is also visible in the centre of 

 the area. In the next stage, a second defining line appears, 

 separated from the former by a narrow band, which is crossed 

 generally by lamellae, but is sometimes occupied in part by 



* Geol. Yorkshire, Part 2. p. 202 ; C. crenulare and C . floriforme ; and 

 for delineations of the former consult pi. 2. figs. 27 & 28. 



