460 Mr. W. Lonsdale on the Genus Lithostrotion. 



Schweigger)*; ^#MiMra,Castelnau; Sty lastrea, Lonsdale?; Colum- 

 naria, Dana (non Goldfuss) ; Siphonodendron ct Nemaphyllum, 

 M'Coy ; Acrocyathus et Lasmocyathus, D'Orbigny. 



"Polypier compose, se multipliant par gemmation laterale. 

 Polypierites entoures d'une epitheque complete, tantot restant 

 libres entre eux lateralement, tantot completement soudes par 

 leurs murailles. Cloisons assez bien developpees. Chambres 

 viscerales presentant dans leurs parties exterieures des traverses 

 vesiculates, et dans leurs parties centrales des planchers bien 

 developpes, qui sont traverses par une columelle styliforme n 

 (p. 432). 



The first species described, Lithostrotion Canadense (p. 433, 

 also explanation of plates, p. 483, with note *), is an American 

 coral ; but the remarks on the genus contain the accompany- 

 ing observation : — " Fleming comprend dans ce groupe quatre 

 especes : la premiere avait dejk ete anciennement nominee par 

 Lhwyd, Lithostrotion, et c'est elle qu'on doit considerer comme le 

 type du genre" (p. 432). In the following remarks therefore, 

 those corals which possess the aggregated composition with the 

 known structures of Lhwyd and Fleming's Lith. striatum will be 

 regarded as the measure of generic comparison. 



Respecting the genera of M. Castelnau and M. D'Orbigny the 

 author can offer no remarks, not being able to consult their 

 works; but Lithodendron, Axinura, Siphonodendron (M'Coy), and 

 Acrocyathus are stated in the ' Archives ' to be synonyms, and to 

 have been separated from the species with laterally united coral- 

 lites only on account of their free or lax habit of growth (" qui sont 

 tons synonymes, et qui n'avaient pour but que de separer les 

 especes a polypierites libres lateralement de celles dont les indi- 

 vidus sont prismatiques et soudes," p. 433). The comparison with 

 Lithostrotion (Lhwyd and Fleming) will be confined therefore to 

 Lithodendron (Phill.), the oldest of the branched genera, to Sty- 

 lastrcat, Columnaria (Dana, not Goldf.), and Nemaphyllum, with 

 remarks on one or two illustrative basaltiform fossils. Only the 

 first of these genera possesses a prevailing branched mode of 

 growth, the others having uniformly corallites which are closely 

 aggregated. The corals forming the Lithostrotion of the { Ar- 

 chives ' are separable therefore into two portions, the first, or 

 equivalents of Lithodendron, consisting of eleven species, and the 

 second of eight ; and they are arranged nearly in conformity with 

 the prevailing habit of growth, though, in consequence of the 

 views of the authors of the monograph, not in distinct sections. 



* In the ' Introduction to the Memoirs on British Fossil Corals/ Litho- 

 dendron of Phillips is retained, hut the Lithodendron of Sehweigger is said 

 not to be " an admissible genus," p. Ixxi. ; see also Appendix A. p. WJ 

 etseg., Geology of Russia, for earlier remarks, 1845. 



