THE ANTHOZOA PERFORATA OF GOTLAND. 11 



when the organic structure is completely changed to a uniform, crystalline limestone ihat 

 it is impossible to make out its identity. 



After comparing the various authors on Silurian fossils, I have no hesitation in draw- 

 ing up the following list of the synonyms of the fossil in question. 



Gen. COENOSTROMA Winchell 



C. DISCOLDEUM Lonsdale. — Porites discoidea Lonsdale in Silurian System p. 688 pl. 

 16 fig. 1. 



Stromatopora constellata Hall, Palaaontology of NewYork Vol. II. p. 324 pl. 72 

 fig. 2. 



Stromatopora concentrica Michelin p. p. Iconographie zoophytologique pl. 49 fig. 4. 

 p. 190. 



Stromatopora polymorpha var. constellata Eichwald Lethasa Rossica p. 346. pl. 22 

 fig. 13 a. b. (fig. 20 pl. 26 is a true Stromatopora). 



Helioiithes? discoideus Duncan in Siluria 4:th Ed. p. 510. 



From this list it is easily seen that this species is widely distributed in' the Silurian 

 beds, and it ranges from the isle of Oesel (Hoheneichen) in the east, över Gotland, probably 

 also över Norway (Christiania) to England (Wenlock) and to the Silurian region of 

 Shoharie in NorthAmerica. 



The Silurian species was succeeded by the Devonian Coenostroma polymorphum so 

 abundantly found in the Eifel mountains, and both are very closely related to each other. 

 It would be worth the while to make out whether many more fossils, numbered amongst 

 the Petrospongia?, although consisting of a calcareous skeleton, be true Spongias or not 

 rather corals of the order Montiporina? or allied to it. There are several described and 

 figured by Mönster, Ladbe, Fromentel and D'Orbigny in their respective works, and the 

 genus Stellispongia of the last mentioned author is in all probability only a congeries of 

 such forms. Thus there is Stellispongia variabilis Munster, (Fromentel Introd. ä letude 

 d. ép. foss. in Mém. Soc. Linnéenne de Normandie Vol. XI. Pl. II. fig. 9) from the Trias- 

 sic strata (»saliférien»), and the genus Actinofungia with the species A. astroites Laube 

 (Die Fauna der Schichten von St. Cassian in Denkschriften d. Ak. Wissensch. Wien 1865 

 p. 243. Tab. II. fig. 6.) also Triassic. But another species of the låter genus, Act. pedicu- 

 lata From. (1. c. p. 49 Tab. IV f. 8) resembles in a still higher degree the Pala-ozoic 

 Coenostroma?, and yet, if I understand M. Fromentel rightly, it is found in strata, so di- 

 stant in ti me, as the LoAver Cretaceous (»etage Néocomien de Germigney»). 



EXPLANATION OF THE PLATE. 



Calostylis denticulata Kjerulf. 

 Fig. 1. Large specimen with lateral buds. 

 » 2. Specimen showing the epitheca. 



