78 G. LINDSTRÖM, HELIOLITIDiE. 



of convex. Of tliis latter structui-e the section fig. 11 is almost entirely coraposed. In 

 the English specimen, fig. 3, being the lowest pai-t of the same as in figs. 1 & 2, the 

 coenenchyraa is nearly free from all vertical elements and composed of lavge, very convex 

 ]amina\ I suppose that the shaded portions of the coencnchyma, fig. 12, vertically streaked, 

 are derived from the walls of the aureola or of the tubnli, occasionally sectioned in a parallel 

 direction or alongside. The dark patches again seen in the transverse sections (fig. 1) and 

 others are due to the convex laminte. 



As a variety of this species I regard a coral from Tjelders in Boge delineated pl. 

 VI, figs. 13 — 15. The aureola is more richly developed with thick, branching radii, covered 

 with larger and more numerous barbs, quite as long as the diameters of the calicle, the 

 septa are nearly of the same conformation as in the former, the coenenchyma of the 

 cancellate fashion which is so predominant in Plasm. follis. It cannot be denied that 

 there exists a wide range of differentiation in this species, when for instance the section 

 fig. 8 is compared with fig. 1 or fig. 10. The septa Avhich are so long in fig. 10 have 

 evidently been destroyed in figs. 1 & 8. The abundant spinosity in the coenenchyma of 

 the latter may in some measure be dependent on its mode of growth, which is somewhat 

 irregular, a great obliquity discernible. As to the great differences in the coenenchyma 

 there are evident transitions from the solely vesicular structure in fig. 3, to that of figs. 

 5 & 9 with aculfe, from that to the more developed quasi tubular or cancellate in figs. 

 2 & 11. This species occurs not rarely at Dudley in England in the Wenlock limestone, 

 more seldom in the strata of Gotland corresponding to the Wenlock shale of England, at 

 the islet Stora Carlsö, and also in the limestone of Simunde, Bara belonging to the stratum 

 /. of Gotland, de Koninck in »Recherches sur les fossiles paléozoiques de la nouvelle 

 Galles du Sud», p. 24, also cites this species as occurring there, but as I have not seen 

 his specimens I do not feel sure of the identity, the more so as his description is very 

 incomplete. 



Plasmopora foroensis n. 



Pl. VI, figs. 16—22, Pl. VII, fig. 1, sections I— IV. 



Corallum disciform or tuberose or grown in irregular, rounded lumps. 



Calides in diameter 2 millim. at the highest, with thick, exsert edge, a little 

 angularly folded in face of the septa. These are of unequal size, long ones reaching near 

 the centre, mixed with much shorter, but \\ithout the alternation, so evident in Heliolites 

 porosus. The centre of the calicle is occupied by the superior ends of lower lying septal 

 spines, which in a section project as some irregular döts (fig. 18). They form no lamina?, 

 but are dissolved into large, closely placed, upwards curved spines (see especially tig. 21). 

 The tabidce are extremely fine or thin, horizontal or wavy and slightly concave. The 

 aureola, is well discernible, though much entangled with excrescences, but attains only 

 half ,the width of the calicle. As the calicles lie close, there is not much space for other 

 coenenchyma and even the aureolas become mixed up with each other. In a longitudinal 

 section the cancellate structure predomimites. The concave lainintij are enclosed between 



