Mr. W. Lonsdale on the Genus Lithostrotion. 467 



corapletement sondes par leurs murailles " (Gen. Char. p. 432) ; 

 provided the expression be rightly understood as applied to 

 those species which are stated to be "massif" or " astreiforme." 

 The existence of an axis is a point of agreement betNveen the 

 branched species {Lithodendra, Phillips) and certain of the mass- 

 ive. Mr. Phillips says, that his fossils have " a prominent cen- 

 tral umbo or axis, generally oval in the section " (Geol. Yorks. ii. 

 p. 202) ; while Dr. Fleming in his account of Lithostr. striatum 

 mentions " a small, solid, central axis " (Brit. Anim. p. 508) ; 

 and in the 'Archives' the only equivalent structure noticed among 

 the generic characters is "une columella styliforme " (p. 432). 

 Whatever may be the intimate composition of these bodies, — and 

 it may be stated, that in Lithod. irreyulare, or in closely allied 

 species, the axis is not solid, but formed of laminae, — they appa- 

 rently agree in presenting a small continuous structure, which 

 to the unassisted eye is nearly uniform in dimensions and com- 

 pactness. It is uncertain whether the Cyathophyllum basaltiforme 

 of Mr. Phillips, and identified by that authority as well as in the 

 ' Archives ' (p. 442) with Lithostr. striatum, has an umbo or axis ; 

 and a similar doubt exists respecting Parkinson's Lithostrotion, 

 likewise considered in the 'Archives' (p. 441) as equivalent to Dr. 

 Fleming's species. Should however the ''prominent star, one- 

 third of the diameter of the" (terminal) "concavity" be regarded 

 as an axis, still the structural composition is markedly different 

 from what is detectable in the umbo of Lithodendra. Allusion 

 is made in a former paragi-aph to a basaltiform coral from the 

 mountain limestone of Kendal, and among other resemblances 

 \isible in transverse, fractured surfaces, to the characters men- 

 tioned by Parkinson, traces of a swelling in the centre of the 

 coralhte are noticed. The direct middle of these projections 

 sometimes exhibited an irregular white spot, or a thickened line 

 formed by the union of opposite lamellae ; and the two structures, 

 in specimens purposely worn down, passed into each other, and 

 often vanished entirely, the absence being evidently not due to 

 decay, but to an altered mode of union in the lamellae. A verti- 

 cal section through the centre gave a very narrow area, occupied 

 by a minute reticulation consisting apparently of the edges of 

 lamellae with transvei-se dissepiments, and not by a compact 

 persistent body. Again, in the Russian fossil, Stylastrea incon- 

 ferta, a styliform axis is manifestly wanting, not from decom- 

 position, but from such a structure never having existed (consult 

 Archives, p. 445, Lithostrotion ? inconfertum) . Prof. ^I'Coy in his 

 description of a British species, Stylast. irregularis, also makes no 

 allusion to an axis ; on the contrary, he says, the centre of his 

 fossil " is remarkable for the nearly perfect transverse chamber- 

 ing " (Ann. and Mag. of Nat. Hist. 2nd Ser. vol. iii. p. 9). The 



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