468 Mr. W. Lonsdale on the Genus Llthostrotion. 



centre of the fossils composing the Columnaria of Mr. Dana "con- 

 sists of oblique septa and cellules converging upwards into an 

 axis ; " and it is further said, that " this axis appears to be made 

 by a convolution of the septa or their partial coalescence " {op. cit^ 

 p. 363; see also pi. 26. figs. 9Z» & 10). Between this structure and 

 the solid axis of Dr. Fleming or of Mr. Phillips^s Lithodendra, 

 there is no resemblance. Nemaphyllum has however " a straight, 

 thin, flat, fillet-like solid, or nearly solid axis" {op, cit. p. 15), 

 which might readily be considered as only a modification of the 

 structure in Lithodendra and Lithostr. striatum,', but an agree- 

 ment in this particular does not by itself warrant a generic 

 union. 



From these statements it appeal's, that among the fossils in- 

 cluded in the Lithostrotion of the * Archives,^ some,^as the species 

 originally described by Mr. Phillips {Lithodendra), the Lithostr,. 

 striatum of Dr. Fleming, and the Nemaphyllum of Prof. M'^Coy, 

 have a " solid" or an apparently compact axis ; while Parkinson's^ 

 fossil and the supposed Kendal equivalent, also the Columnaria 

 of Mr. Dana, have a large central projection of lax composition;, 

 and in Stylastrea as well as in Cyathophyllum basaltiforme, the 

 existence of an axis cannot be afiirmed. An agreement,, as before 

 mentioned, occurs therefore in certain branched and one massive 

 or basaltiform species, omitting Nemaphyllum on account of its 

 inseparable corallites ; nevertheless the accordance does not con- 

 stitute a generic identity even in the fossils in which it exists. 



The next structure claiming attention is that which sui-rounds 

 the axis., Mr. Phillips does not describe its composition; but 

 his delineations of vertical sections {op. cit. pi. 2. tig. 17 & 19), 

 possibly intended only as diagrams,, exhibit simple laminre in- 

 clined upwards and resting against the axis ; though in the spe- 

 cimens examined they were often complex ; occupying, however, 

 as in the figures just quoted, a broad band on each side of the 

 slender central body. In the ' Archives ' the " visceral chambers " 

 are stated to present " dans leurs parties centrales des planchers 

 bien developpes, qui sont traverses par une columelle styliforme" 

 (p. 432). The transverse sections which were examined afforded 

 diversity of character, according to their position with res])ect to 

 the upturned laminse. Sometimes the axis was surrounded by 

 a clouded, ill-defined band, marking apparently a coincidence in 

 the plane of cutting with the surface of one of those lamina?; 

 occasionally an open zone occiu-red traversed by irregular, curved 

 lines ; and not unfrequently lamellpe ranged up to. the axis. 

 The equivalent portion of Lhwyd^s coral is unknown; and Dr. 

 Fleming in his account o^ Lithostr. striatum simply mentions the 

 union of "the rays of the star" with a small solid axis — only 

 tiue of the conditions in Lithodendra. The central projection in. 



