456 Mr. W. Lonsdale on the Genus Lithostrotion. 



arched lamina?. At first, the line and band are limited to the 

 free side of the young corallite, or that fronting the mature 

 centre, and the line is united at each extremity with the wall of 

 the parent. As however the offspring increased, the portion be- 

 fore stated to be in contact with the pre-existing mature boun- 

 dary is separated ; and an interspace is laid open, perfecting the 

 range of the narrow band ; while the second defining line is com- 

 pleted by an upward extension, on that side, of the old wall, or 

 by an equivalent structure. In this state, the first-formed limit 

 constitutes the partition between the lamelliferous and vesicular 

 zones, and the second is the permanent wall of the added coral- 

 lite. Remarks on further advanced conditions are unnecessary. 

 Among the Russian polyparia before mentioned, four species of 

 Lithostrotion are described*, three of which were believed to be 

 new, and one to be identical with the L. floriforme of England. 

 They all displayed fully the triple composition of the Derbyshire 

 and Clifton fossils ; and the first noticed species exhibited a suffi- 

 cient number of young corullites within the boundary of the pa- 

 rent to prove that such was the essential mode of reproduction 

 (p. 605) ; in the third species, L. astro'ides, a decided instance 

 was also noticed (p. 608) ; and in the foui'th, L. floriforme, cases 

 were likewise believed to have been detected (p. 610) ; but in the 

 second species, L. manimillare, " the young columns projected 

 irregularly above the general surface, and in positions wdiich 

 rendered it difficult to imagine that they could have been in a 

 young state included within the areas of the adjacent mature 

 columns " (p. 607). The foregoing statements will, it is hoped, 

 justify the conclusion drawn in 1845 respecting the prevalent 

 n)ode of developing additional corallites in the fossils assigned to 

 Lithostrotion. Many instances will occur to every collector in 

 which it will be difficult to decide on the real mode ; and if only 

 such be accessible, they would lead to a different conclusion from 

 that at which he has arrived. He begs to add, that he does not 

 rest on the reproductive process alone for the establishment of 

 Lithostrotion as defined in the Appendix before quoted. 



It is now necessary, in order to show still further the uncer- 

 tainty of the fossil originally termed Lithostrotion, to offer a few 

 additional observations on carboniferous basaltiform corals. It 

 has been already stated, that in the work on Russia by Sir R. I. 

 Murchison, M. Ed. de Verneuil, and Count A. von Keyserling 



* Count A. von Ke5'serling has united the four corals under one species, 

 Lith. floriforme, l>ut it is ho])ed that a careful consideration of the detailed 

 characters will justify the original conclusions. He also includes Stylastrea 

 in Lithostrotion ; nevertheless the points of difference, noticed in a para- 

 graph of this communication, are considered sufficient to justify a generic 

 separation. (Reise in das Petschora-Laud, pp. 152 & 154, 1846.) 



