454 Mr. W. Lonsdale on the Genus Lithostrotion. 



Lhwyd's fossil, though all three have been identified with it. A 

 similar impression induced the author of this notice, when he de- 

 scribed the corals collected by Sir R. I. Murchison in llussia in 

 Europe and the Ural Mountains*, to state that Lhwyd's coral 

 " has probably been mistaken in some cases for other fossils of 

 similar general aspect, yet of very different structure ;" and as 

 a subdivision of Dr. Fleming's genus appeared necessary, he 

 adopted as the type of Lithostrotion that authority's second spe- 

 cies, being " a well-known, strongly marked coral, and excel- 

 lently figured by Martin in his f Petrificata Derbiensia ' " (op. cit. 

 p. 603). In a subsequent portion of that Appendix (p. 619), the 

 describer applied the term Stylasti*ea to certain corals, which he 

 considered referable to Parkinson's fossil ; and if he erred, as he 

 feels he did, in positively identifying, on insufficient data, the 

 latter with Lhwyd's delineation, the admission of the error only 

 leaves still more doubtful the actual nature of that body. In 

 retaining the term Lithostrotion for the second species of Dr. Fle- 

 ming, who it must be remembered really established the genus, 

 and in suggesting a new designation for corals w T hich bear only 

 a certain resemblance to the first species, the author believes he 

 acted in conformity with one of the rules laid down by the Com- 

 mittee of the British Association appointed to prepare " A series 

 of propositions for rendering the nomenclature of zoology uni- 

 form and permanentf." According to that rule, " When the evi- 

 dence as to the original type of a genus is not perfectly clear and 

 indisputable, then the person who first subdivides the genus may 

 affix the original name to any portion of it at his discretion, and 

 no later author has a right to transfer that name to any other 

 part of the original genus" (op. cit. infra, p. 264. § 5). 



Martin's delineation (Pet. Derb. t. 43. f. 3), though taken from 

 a limited fragment, expresses so completely the general characters 

 of the fossil, that in the examination of a collection of Derbyshire 

 zoophytes no mistake could be made in identifying a specimen, 

 should one occur. The essential characters given in the Ap- 

 pendix before mentioned are — " stems generally coadunated ; in- 

 terior of stems separable into three differently constructed areas : 

 1. a central axis ; 2. an inner zone composed of vertical lamellae; 

 3. an outer zone formed partly of lamellae, but chiefly of variously 

 arched or vesicular plates : the mode of reproduction " is further 

 said to have been " by germs developed within the area of the 

 parent stem, or without it by an occasional extension of the po- 



* Geology of Russia in Europe and the Ural Mountains, by Sir R. I. Mur- 

 chison, M. Ed. de Verneuil, and Count Alex, von Keyserling, vol. i. App. A. 

 p. 602 et seq., 1845. 



t Annals and Magazine of Natural History, 1st Series, vol. xi. April 1843, 

 p. 259 et seq. See also Report of the British Association for 1842, p. 105 



