SPIRIFERA. 49 



Obs. Although a description of Martin's Jnomites subconicus is here appended, and 

 which is taken from the original figure published in the ' Petrificata Derbiensia,' I am 

 far from satisfied that the specific characters or claims of the species have been clearly 

 established, and the more so since no other example could be discovered in our English 

 collections. In 1843, Professor L. de Koninck described and represented -i^. septosa, 

 Phillips, under the erroneous denomination of Sp. subconicus, Martin, from being at the 

 time unacquainted with the British types of either species ; but a few years later my 

 friend had discovered his mistake, and he is now of opinion that Martin's figure may, 

 perhaps, have been drawn from some exceptional specimen or variety of Cmpidatus. 

 This may possibly prove a correct interpretation, although I am not at present acquainted 

 with any example of the last-named species with quite so small a number of ribs, but we 

 are all aware how much the specimens of the same species may vary in this particular. 

 Martin observes that the difference between his two species is in the number of 

 furrows or ribs, which in Subconicus are few and acute, the central rib or fold being 

 angular instead of a rounded wave in the margin, and the beak of the conic valve 

 is straight or not recurved, as in Cusjndatus ; but had the author of the ' Petrificata 

 Derbiensia' possessed a larger number of his own Cuspidatus he would soon have perceived 

 the little real importance of the above distinctions. 



Martin states that his fossil was found in the carboniferous limestone of Middleton, 

 where the shell is said to be verj/ rare. 



Spirifera triradialis, Phillips. Plate IX, figs. 4 — 12. 



Spirifera triradialis, Phillips. Geol. of York., vol. ii, p. 219, pi. 10, fig. 7, 1836. 



— TRisuLcosA, Phillips. Ibid., pi. 10, fig. 6. 



— SEXRADiALis, Phillips. Ibid., fig. 7. 



— TRISULCOSA = TRIRADIALIS, De Koniuck. Descrip. des Animaux Fossiles de la 



Belgiqne, p. 266, pi. xvii, fig. 7, a, b, c, 1843. 



— SEXRADIALIS, M' Coy. British Palseozoic Fossils, p. 421, 1855. 



Sprr. Char. Circular or longitudinally oval ; dorsal valve slightly convex, mesial fold 

 smooth and sharply defined with two, fom*, or six rounded ribs on either valve ; but when 

 two or four only the remaining unoccupied lateral space is smooth. Ventral valve much 

 deeper than the opposite one, with a sinus extending from the extremity of the beak to 

 the front ; beak moderately produced ; hinge line not longer than about half the width of 

 the shell. Cardinal angles rounded ; area small, triangular, with its margins not always 

 sharply defined, so that the lateral portions of the beak are visible on either side; fissure 

 large and partly covered by a pscudo-deltidiura. Numerous concentric lines of growth 

 cover the surface of either valve. The dimensions are very variable, those taken from 

 four specimens have produced — 



7 



