218 BRITISH CARBONIFEROUS BRACHIOPODA. 



Ohs. This interesting species has much resemblance to Phillips' Devonian Spirifera 

 pltalana, 1 as well as to De Verneuil's Terebrattda Hispanica from the Devonian rocks of 

 Spain, 2 and for some time I felt disposed to consider the form under description as a 

 variety of Phillips' species, but after comparing three examples of our carboniferous shell 

 with the figures of the Devonian species, it appeared to me that our shell was more sub- 

 rhomboidal in shape, and had not the straight hinge line of the Devonian species ; the 

 sinus in S. pit al ana and T. Hispanica is also much wider and deeper than what we find in 

 our shell, and the mesial fold is also much more deeply divided. I have therefore named 

 the carboniferous species after its discoverer, and as an appreciation of the valuable assist- 

 ance I have received from him during my examination of the many Staffordshire species 

 he had so zealously collected. Mr. Carrington has obtained eight or nine specimens from 

 the carboniferous limestone of Wetton, in Staffordshire. 



Retzia. 



Two species have been already described, and a third has recently been found. 



Retzia radialis (p. 87). Plate XVII, figs. 19—21, and Plate LI, figs. 4—9. 



This shell appears to have varied considerably in shape, as well as in the number and 

 size of its ribs, so much so that many of its variations when viewed individually, might 

 lead us to doubt their being simple modifications of Phillips' type. After having 

 assembled a great many specimens from the same as well as from distinct localities, I soon 

 perceived that extreme forms, with twenty-three small ribs, and those with eleven large 

 angular ones upon each valve, could be easily connected by intermediate links ; that, for 

 instance, some examples possessed thirteen ribs, others seventeen, nineteen, and twenty-one. 

 In some localities, likewise, owing no doubt to peculiar circumstances, the shells were all 

 small, while in other places they have attained half an inch in length. In PI. LI, as 

 well as in PI. XVII, will be found illustrations of all the most marked variations in 

 form hitherto observed. 



Retzia ulotrix (p. 88). Plate XVIII, figs. 14, 15. 



This appears to be a rare species ; a very perfect example has, however, been recently 

 discovered by Mr. Carrington in the carboniferous limestone of Allstouefield, in 

 Staffordshire. (PI. LIV, fig. 45.) 



1 Figures and descriptions of the Palaeozoic fossils of Cornwall, Devon, and West Somerset, p. 71, pi. 

 xxviii, fig. 123, found at Hope, near Torquay. S. phalcena belongs to the genus Athyris, not Spirifera. 



2 'Bulletin de la Soc. Geol. de France,' 2d serie, Tom. 2d, p. 4C3, pi. xiv, fig. 7. Mr. de Verneuil's 

 T. Hispanica, belongs to the genus Athyris, and is perhaps a synonym of A. phahena . 



