Mr. W. Lonsdale on the Genus Lithostrotion. 451 



XXXVII. — Note on the Genus Lithostrotion. 

 By William Lonsdale, F.G.S. 



To the Editors of the Annals of Natural History. 



Gentlemen, 



Should the following memoranda on the genus Lithostrotion be 

 deemed admissible, I shall feel obliged by their publication in 

 the f Annals and Magazine of Natural History/ 



I have the honour to be, Gentlemen, 



Your most obedient servant, 

 Melksham, Nov. 1851. W. LpNSDALE. 



Lhwyd* is well known to have applied the definition, u Litho- 

 strotion sive Basaltes minimus striatus et stellatus," to a coral 

 represented in table 23 of his work on British Fossils ; but no 

 farther description of it is given in the chapter on coralline 

 stones or in Letter Five (op. cit. p. 122). The rude delineation, 

 just quoted, expresses fully an aggregate of polygonal columns 

 longitudinally striated and transversely rugose; the upper sur- 

 face presents also closely applied stellated areas variable in size 

 as well as in the number of the facets, but uniformly traversed 

 by many converging, fine rays. The limited amount of informa- 

 tion thus communicated renders a satisfactory comparison with 

 other basaltiform and lamelliferous Zoantharia hazardous; but 

 Parkinson t identified a Welch coral with Lhwyd' s Lithostrotion , 

 and he describes it as composed " of polygonal columns, exactly 

 adapted and closely concreted " (p. 43) ; but detachable from the 

 general mass " by a moderate stroke " applied laterally (p. 44) ; 

 the facets of the columns are moreover stated " to be finely and 

 closely striated longitudinally, the striae being intersected by very 

 fine and closely set transverse ridges '■ (p. 44). Complete apices 

 are also said to be " concave and to have a prominent star, one- 

 third of the diameter of the concavity, arising out of the centre n 

 (p. 44). A longitudinal section is further described as having 

 " a striated plumose appearance " (I. c.) ; and allusion is made 

 to " numerous, exceedingly slender longitudinal lamellae, cor- 

 responding with the external striae ; " also to " equally delicate 

 lamellae perpendicularly disposed nearly in concentric circles; 

 while others answering to the external transverse ridges," are 

 stated to pass horizontally through both of the perpendicular 

 sets (p. 44). Parkinson gives therefore a considerable amount 



* Lithophylacii Britaimici Ichnographia, edit. 1699. 

 t Organic llemains of a Former World, vol. ii. p. 43-44, pi. 5. figs. 3 

 and 6, 1808, reprinted 1833. 



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