chief Generic Types of Palaeozoic Corah. 297 



The genus Petalaxis, E. & H,, lastly, has been but im- 

 perfectly defined (Brit. Foss. Cor., Intr. p. Ixxi, under the 

 name of Nematophyllum) ; and it seems difficult to determine 

 precisely what characters its authors wished to assign to it. 

 So far, however, as can be judged from the descriptions and 

 figures of the two species * embraced under this name (viz. 

 P. M'Coyana, E. & H., and P. Porflocki, E. & H.), the genus 

 would not appear to be separated by sufficient characters from 

 LitJiostrotion proper. 



With the exception of a single species [L. antiqmim^ Bronn), 

 which is believed to be of Devonian age, all the known species 

 of Lithostrotion are referable to the Carboniferous period, where 

 they constitute one of the most a})undant and characteristic 

 groups of corals. 



Genus KONINCKOPHYLLUM, Thomson and Nicholson. 



Gen. char. Corallum simple or compound. Septa well 

 developed, but not reaching the centre, united externally by 

 numerous delicate dissepiments, which give rise to an exterior 

 zone of dense vesicular tissue. Tabulae occupying a central 

 area of considerable size, into which the septa are only very 

 partially, or not at all, continued. A styliform, compact or 

 subcompact columella. Occasionally a septal fossula. In the 

 compound forms increase is by calicular gemmation. 



We have believed ourselves justified in founding this genus 

 for the reception of certain corals from the Carboniferous rocks 

 of Scotland, which present a combination of characters pecu- 

 liarly their own, and which may be regarded as, in some 

 respects, intermediate between GyathophyUum and Lifhostro- 

 tion. We have named the genus in honour of Prof, de 

 Koninck, whose work amongst the Paleozoic corals has so 

 deservedly contributed to the high reputation which he has 

 obtained in various branches of palaeontology 



The corallum in Koiiinckophyllum is sometimes simple, and 

 sometimes compound. When simple, it is usually of small 

 size, rarely exceeding two inches in length, and it is conical, 



* These species were originally described by Milne-Edwards and Hainie 

 (Pol. Foss. p. 453) under the names of Stylaxis 31' Coyana and S. Port- 

 locki, and were transferred subsequently to Petcdaxk (Brit. Foss. Corals, 

 p. 205). Under anj^ circumstances, these species must not be confounded 

 with the forms known as Lithostrotion M' Coyanum and L. Purtlocki, Bronn. 

 These latter are entirely distinct from the former, and are retained in Litho- 

 strotion in the last grouping of the genus proposed by Milne-Edwards and 

 Haime. If Petalaxis be abandoned and relegated to Lithostrotion, then the 

 specific names of M' C'o//rt;/a and PojV/or^-j applied to the two species ot 

 the genus will have to be changed. 



Ann. & Mag. N. Hist. Ser. 4. Vol. xvii. 20 



