KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 32. N:0 I. 77 



Plasmopora petaliforims. Lonsdale. 

 Pl. vr, figs. 1—12. 



1839. Porites petnlliformis LONSBALE. Sil. Syst. II, p. 687, pl. 16, figs. 4, 4rt. 



1849. Plnsraopora petalifovmis Edw. & H. Comptes Rendus, vol. XXIX, p. 262. 



1850. :> s IlD. Br. Foss. Cor. Iiitrod., p. Ux. 



1851. Palieopora petalliformis M'COY. Brit. Palneoz. Foss., p. 17. 

 1851. Plasmopora petaliformis Edw. & H. Pol. pal., p. 221. 



1854. » » IlD. Brit. Sil. Cor., p. 253, pl. LIX, fio-s. l, \n, nnt tig. Ih wliich belongs to 



the new species Plasmop. stella. 

 1860. » » IlD. Hist. Nat. Cor. III, p. 240. 



? 1862. Porites petalliformis M'COY. Sil. Foss. Ireland, p. 62, iiucertain wlietlier identical. 

 1867. Plasmopora petaliformis LiNDSTR. jS^oin. Foss. Gotl., p. 27. 

 1867. » (Heliolites) » Ddncan. Siluria, pl. 39, f. 4. 



1879. » » QUENSTEDT. Petref. Deutsclilands, p. 152, Taf. 149, f. 11. 



1880. » » NiCHOLSON & Etheridge. Girvan, p. 267, Fig. A, but not in iTabulate Coralss, 



pl. XI, f. 5 and pl. XII, f. 1, which differ in having no septa. 

 1883. » » Fbrd. Roemer. Letli. Geogn., p. 510, fig. 121 a — h. The last fignre is in so 



far inexact that tlic septal spines are not deliueated. 

 1883. » » VON KOCH. Palseoutogr., p. 334, pl. 43, figs. 12—15. 



1885. s » LlNDSTR. List. Foss. of Gotland, p. 18. 



1888. » » ID. List. U. Sil. Foss. Sweden, p. 21. 



The English specimens have grown in regularly scmiglobular disks of circular circum- 

 ference, with tlie superior surface convex, hollow or flaitened on the basal side, which is 

 concentrically, coarsely wrinkled by a thin epitheca. The Gotlandic specimens are more 

 irregular, forming larger disks of moderate thickness. 



The calicles have a diameter varying between two and one millimeter according to 

 the specimens. The edge is rather oftener essert than immersed. 



The seiyta are variable in length (fig. 7), though usually long (fig. 10) and straight. 

 In sections (figs. 1, 4) they are often destroyed and shortened. They have no large lamina 

 (figs. 9, 12 etc), are divided into spines, more or less curved, which do not reach to the 

 centre of the calicle. The tabulce are sparse, thin irrcgularly concave. 



The aureola surrounding the calicle is of varying width, with radii as long as the 

 diameter of the calicle or even only as half that size. The radii may be crooked or 

 straight, often with barbs on both sides. The compartments between the radii are of the 

 same width near the theca as at their outward edge, only a little widening. The coenen- 

 chymal tubes are much irregular, especially as to their size, and upon the whole they 

 are rather scarce, as the space between the calicles is chiefly occupied by the aureolse. 

 It is difficult to find how this vertical part of the corallian sceleton is placed in relation 

 to the vesicular tissue of the coenenchvma. There are aculfc, ordinate in longitudinal 

 rows (figs. 5, 9), these have coalesced (fig. 12 at the right in the coenenchyma), forming 

 two zigzaglines enclosing modified bladders, becoraing nearly square or flattopped instead 



K. Sv. Vet. kVai. IlaiiJl. Baud 32. N:o 1. 10 



