698 



SILURIAN FUCOIDS. 



Unable to acquire more knowledge concerning the affinities of this fossil, I simply refer to 

 the figure, in which the beautiful tesselation of its surface is expressed ; and feeling that any 

 name, which does not mislead, is better than no name, I have called it Ischadites, from tcr%a?, 

 a dried or potted fig, the specific name being furnished by my friend Mr. Konig, who, as above 

 stated, has described animals somewhat analogous. (See Leucophthalmus, Icones Fossiles, 

 Cent, l. f. l.) 



Loc. Ludloiv (Lower Ludlow Rock). Found by Dr. Lloyd, to whom I am so deeply indebted 

 for many of the fossils engraved in this work 1 . 

 Polymeres Demetarum, PI. 26. f. 13. 



This fossil, which occurs in dull black shale with the Ogygia Murchisonice, PI. 25. f. 3, 

 consists of a cylindrical, longitudinally divided tube, cut transversely into short pieces or seg- 

 ments, the edges of which are inclined. The joints are parallel and cylindrical, and instead of 

 forming regular circles, are bent into several arcs : both surfaces are smooth. The tubes in 

 various specimens are crushed transversely, obliquely, or longitudinally according to their po- 

 sition in the rock, and in the same direction as the trilobites and other organic remains of the 

 mass. As the segments appear to be entire cylinders, the tubes may be the remains of ani- 

 mals resembling lulus or Oniscus. It is probable that the matrix was once filled with pyrites, 

 which in decomposing has left only black oxyd of iron and stellated groups of crystals of 

 gypsum. 



Loc. Pensarn or Mount Pleasant on the left bank of the Towy, near Caermarthen. 



These tubular bodies were discovered with the Ogygia Murchisonice in the above locality. 

 I have named them after the county in which they occur 2 . 



FUCOIDS. 



To the figures of fossils, whose place in the natural kingdom is not easily determined, I might 

 have added the drawings of certain indistinct fucoids. The best preserved, however, of these spe- 

 cimens does not express more than the small figure already given by Mr. Yates in the Transactions 

 of the Geological Society, vol. ii. New Series, PI. 27. The specimens I collected were examined 

 by Mr. Robert Brown and Dr. Greville, but neither of these eminent botanists are able to say much 

 more than that they are fucoid-like bodies. 



They chiefly occur in Caradoc Sandstone, or in the beds of passage between that formation and 

 the Wenlock Shale. They are found in the latter position on the eastern side of the Lower Lickey 

 Hills, and in true Caradoc Sandstone at Ankerdine Hill, Worcestershire : the species at these two 

 localities are distinct. 



1 The Cornularius Serpularius, Schloth., of the Wenlock Limestone, and of which four figures are given PI. 26. 

 figs. 5 to 9. is fully described, p. 627, though without being placed in its natural position in the animal kingdom. 

 In like manner, the Tentaculites, Schloth., of which four species are described, pp. 613, 628, 643. PI. 5. f. 33. 

 PL 12. f. 25. PI. 19. figs. 15 and 16., is not yet referred to any known animal, and is therefore arranged in 

 the general table with the other forms whose place is uncertain. 



2 Demetee, Caermarthenshire. 



