SPIRIFERA. 223 



as from twenty to thirty occupying the width of three lines, and of which an enlarged 

 representation will be found in PL L, fig. 9". 



Spirifera convoluta, Phillips (p. 35). Plate V, figs. 9—15 (2 to 8 excluded); and 



Plate L, figs. 1, 2. 



J o~ 



This appears to be a rare species, of which three or four very remarkable speci- 

 mens have been found by Mr. J. Rofe, at Thorneley, near Chipping (ten miles N.E. 

 of Preston). One specimen in particular (PI. L, fig. 1) was perfect from end to end, and 

 measured eleven lines in length by fifty-seven in breadth, and twelve in depth. The shell 

 occurs also in the carboniferous limestone of the neighbourhood of Wetton, in Staffordshire. 

 I fear having too hastily coincided in the view taken by Prof, de Koninck, that Sp. rhom- 

 boidea (Phillips) was a synonym of S. convoluta. Mr. E. Dupont states he has found S. 

 convoluta abundantly at Celles, near Dinant, in Belgium. 



Spirifera rhomboidea, Phillips. Plate V, figs. 2 — 8. 



Prof. Phillips's description of this species will be found in the foot note of p. 36. A 

 great difference is observable in the mesial fold and sinus of all the specimens I have seen 

 of this and the preceding species. In Sp. convoluta it resembles much that of Sp. 

 trigonalis, its three principal ribs being strongly marked, while in Sp. rhomboidea they are 

 more numerous, and hardly defined. 



Spirifera triangularis, Martin (p. 27). Plate V, figs. 16 — 24; and Plate L, figs. 



10—17. 



This is a very elegant and well-characterised species, easily distinguishable, but 

 extremely difficult to extract from the hard limestone matrix in which it is usually 

 imbedded : nevertheless, after much labour, Mr. Burrow has been able to procure a 

 numerous series, among which were several, examples that retained their elongated 

 tapering wings quite perfect ; but it is remarkable that when one wing became very much 

 prolonged, the other was somewhat suddenly abbreviated, and this is very clearly discernible 

 in the two or three of the most perfect specimens hitherto discovered (PI. L, figs. 13, 15, 16). 

 It is also necessary to remark, that in young shells the front was not very much produced, 

 while in the adults the acutely angular cuneiform rib in the fold and sinus projects con- 

 siderably above and beyond the regular surface of the valve (PI. V, fig. 21). 



