202 BRITISH FOSSIL CORALS. 



"Tubes averaging 6 lines in diameter, mostly hexagonal; external surface coarsely 

 striated longitudinally, and transversely marked with strong curved irregularities of 

 growth, the convexity of the curves upwards ; horizontal section, 63 slender radiating 

 lamellae, converging from the walls towards the flat central style or axis, which is about 

 one line in width ; one half of the lamellae reach the centre, the intervening ones reach 

 rather more than half way ; outer area exhibiting numerous transverse vesicular plates 

 between the radiating lamellae. 



" Vertical section, axis straight, riband-like, inner area broad, of slightly-curved 

 vesicular plates, forming rows of lengthened irregular cells, extending obliquely down- 

 wards and outwards from the axis, about three in a row ; outer area of rows of small, hemi- 

 spherically-curved plates, including small, rounded cells, extending very obliquely up- 

 wards and outwards, about 5 or 6 in each row. 



" From the carboniferous limestone of Derbyshire." (M'Coy, op. cit.) 



16. LlTHOSTROTION ARACHNOIDEUM. 



Nemaphylltjm auachnoideum, M'Coy, Ann. and Mag. of Nat. Hist., 2d series, vol. iii, 



p. 15, figs, a, b, and p. 16, 1849. 

 Stytlaxis arachnoidea, Milne Edwards and Jules Haime, Pol. Foss. des Terr. Palaeoz., 



p. 454, 1851. 

 Nematophyllum aPvACHNOIdeum, M'Coy, Brit. Palaeoz. Foss., p. 97, pi. iii a, fig. 6, 1851. 



" Stars, with from four to seven angles, and averaging from 6 to 9 lines in diameter; 

 axis very thin, 1 line wide ; vertical section, inner vesicular area wider than the outer of 

 little arched plates, inclining slightly downwards from the axis ; it takes about two (rarely 

 one) of those plates to reach from the axis to the extent of this area, or two irregularly 

 elongate, unequal cells in a slightly oblique line, from the axis to the wall of the inner 

 area; outer area separated from the inner by a sharp, distinct line on each side, and 

 composed of much smaller and more highly curved vesicular plates, so that there are from 

 5 to 7 small, nearly equal, rounded cells, extending in a line obliquely upwards and out- 

 wards, from the inner area to the outer walls of the tube ; horizontal section, boundary or 

 divisional walls thin, stars radiated with from 50 to 55 very thin lamellae, of equal thick- 

 ness, but alternately long and short, the long reaching to the centre, the short barely 

 entering the edge of the inner area ; weathered surface, stars flattened, separated by a 

 depressed line; inner area forming a gentle convex, oval, or circular boss, with the axis 

 forming a short impressed line in the middle; the radiating lamellae exhibit numerous 

 delicate, curved, interstitial plates in the outer area, but none in the inner area. 



"Forms large masses in the carboniferous limestone of Derbyshire." (M'Coy, op. cit.) 



