47G Mr. W. Lonsdale on the Genus Lithostrotion. 



it is believed that their absence is a true distinction between the 

 branched species or Lithodendra and the massive corals enume- 

 rated among the synonyms of the preceding list, so far as their 

 composition is known, with the exception of Lithostrotion micro- 

 Ithyllum (No. 13) given with a doubt, and Nemaphyllum minus 

 (No. 14) ; in both of which an intermediate zone of arched 

 laminae exists similar to the plates in Lithodendra. It is also 

 conceived, that the omission of the mode of increase in Lithostr. 

 basaltiforme is correct, nothing being known respecting it in the 

 fossils quoted as synonyms, except that in L. microphyUum 

 (No. 13) new prisms were planted on the edges between the old 

 corallites (" durch Einsenkung neuer Prismen in den llandern 

 zwischen den altercn " — Reise in das Petschora-Land, p. 156) ; 

 and in the generic characters of Nemaphyllum {N. minus, No. 14), 

 additions are stated to have been effected by " small circular buds 

 developed within the area of the parent star " (Ann. and Mag. 

 Nat. Hist. 2nd Ser. vol. iii. p. 15, and woodcut). The "colu- 

 melle petite, comprimee, mais un peu renflee au milieu " (Ar- 

 chives, p. 442), agrees with the "columelle styliforme" of the 

 generic characters (p. 432), and with the " small solid axis " of 

 Lithostr. striatum ; also to a certain extent with the central struc- 

 ture of Nemaphyllum minus (No. 14), and possibly with that of 

 Astrea hexagona (No. 10) ; but there are no grounds for con- 

 cluding that a similar axis occurs in Parkinson^s Lithostrotion 

 (No. 2), or in Cyathophyllum basaltiforme (No. 8), or perhaps in 

 Lithostr. microphyUum ? (No. 13). Again, the "polypierites" are 

 said to be " completement sondes par leurs murailles " (p. 442), 

 by which the author understands that they are so united as to be 

 inseparable with smooth exteriors. In the remarks on the mode 

 of union, given in an eai'ly part of this communication, a want 

 of positive information on this point is mentioned as respects the 

 original fossils of Lhwyd (No. 1) and Parkinson (No. 2) ; though, 

 from the facility with which the corallites in No. 2 separated 

 (Org. Hem. t. ii. pp. 43, 44), it may be inferred that an inti- 

 mate union did not exist. On the contrary, in Astrea hexagona 

 (No. 10), Lithostrotion microphyUum (No, 13), and Nemaphyllum 

 minus (No. 14), a perfect union is apparently maintained. Not 

 one of the fossils included under the head L. basaltiforme, so far 

 as is known from descriptions or delineations, ever assumes the 

 branched habit of growth of Lithodendra. 



Very little remains to be said. The fourteen quotations con- 

 tained in the foregoing list include seven distinct fossils, which 

 are numbered 1, 2, 4, 8, 10, 13 and 14, the remaining seven, 

 Nos. 3, 5, 6, 7, 9, 11 and 12, being only references to Lhwyd, 

 Parkinson and Phillips, without any increase of structural de- 

 tails except in the case of No. 5, Dr. Fleming's L. striatum. Of 



