6 BRITISH STROMATOPOROIDS. 



more briefly summarise the history of the group since the appearance of the 

 ' Petrefacta Germanise ' in 1826. 



In the year 1833, de Blainville referred Stromatopora, with some doubt, to the 

 Corals (' Manuel d'Actinologie,' p. 413). 



In 1834, Steininger (' Mem. de la Soc Geol. de France,' torn, i) described some 

 species of Stromatoporoids from the Bifel Limestone. One of these, which he 

 termed Alcyonium echmatwm, has been generally identified with Actinostroma 

 {Stromatopora) verrucosmn, Goldf. The genus Stromatopora was referred by 

 Steininger to the Sponges. 



In the 'Silurian System' (1839), Mr. Lonsdale gave a list, accompanied by 

 figures, of the Silurian Corals, and among these he described two species of 

 Stromatoporoids under the names 8. concentrica, Goldf., and 8. nummulitisimilis, 

 Lonsd. The former of these cannot be certainly identified from the description 

 and figure given (' Sil. Syst.,' p. G80, pi. xv, fig. 31), there being at least two 

 species in the Wenlock Limestone of Britain, which might have served as Lons- 

 dale's type. An examination, however, of Lonsdale's original specimen, now 

 preserved in the British Museum, shows it to be really one of the most beautiful 

 and characteristic of the Wenlock Stromatoporoids, and properly referable to the 

 genus Glathrodictyon. As d'Orbigny subsequently named Lonsdale's species 

 Stromatopora striatella, this form will now stand as Glathrodictyon striatellum, 

 d'Orb. sp. The second form described by Lonsdale, viz. 8. nummulitisimilis, is 

 not organic, but was founded upon specimens of the pisolitic limestone which forms 

 part of the series of the Wenlock Limestone at Colwell, near Ledbury. 



In addition to the above, Lonsdale described and figured a third Stromatopo- 

 roid from the Wenlock Limestone, under the name of Porites discoidea (' Sil. Syst.,' 

 p. 688, pi. xvi, fig. 1). The true nature of the fossil so named certainly could not 

 have been recognised from the description or figure given of it ; and it is not 

 surprising that in the later editions of ' Siluria ' it should have been doubtfully 

 placed under Heliolites. The original specimen of Porites discoidea, Lonsd., now 

 in the British Museum, can, however, be at once shown to be, as long since 

 surmised by Lindstrom, a genuine Stromatoporoid. The internal structure of the 

 figured specimen has been, unfortunately, so far destroyed by secondary crystal- 

 lisation that thin sections yield no conclusive evidence as to its true nature and 

 affinities. Judging, however, from its external characters, there can be little 

 hesitation in identifying the species with the form described by von Rosen under 

 the name of Stromatopora elegans. This is a true Stromatopora, Goldf. (in the 

 sense previously defined), and the species will therefore stand as Stromatopora 

 discoidea, Lonsd. sp. 



In 1840, Mr. Lonsdale published some further observations on the Stromato- 

 poroids (' Trans. Geol. Soc. Lond.,' ser. 2, vol. v). He placed the genus Stromato- 



