16 BRITISH PERMIAN BRACHIOPODA. 



width of the shell ; cardinal angles rounded, area triangular, fissure large and partly con- 

 cealed by a pseudo-deltidium ; beak rounded and elevated. The dorsal valve is but slightly 

 convex, with a mesial depression or furrow, commencing at a short distance from the 

 moderately inflated umbone, and extending to the front ; it also possesses a small trian- 

 gular area. The ventral valve is by far the deepest and most convex, with a mesial furrow 

 originating at a short distance from the extremity of the beak, and extending to the front. 

 The external surface of the shell is covered with numerous closely set and inclined hair- 

 like spinules. 1 In dimensions it does not in general exceed — length 2, width 2, and 

 depth 1^ lines. 



This interesting little species appears to be so closely related to the Carboniferous 

 Sp. Urei of Fleming, 2 as well as to the Devonian Sp. nnguiculata of J. de C. Sowerby and 

 Phillips, 3 that I am still uncertain whether it is in reality distinct, or simply a variety or 

 race slightly modified by time? After a minute examination of some well-preserved 

 examples of Sp. Urei, which I had obtained through the kindness of Dr. Fleming and 

 of another friend in Scotland, and having ascertained that they had been likewise covered 

 with spinules, I requested Professor King to compare my Carboniferous specimens with 

 those of his Permian shell, and he has transmitted the following observations : " Sp. Urei 

 and Sp. Clannyana are, I am decidedly of opinion, distinct species, though apparently 

 allied to each other. Urei differs from Clannyana in being a wider shell ; it has the 

 umbone more incurved, the area of the small valve not so deep. The dorsal valve is more 

 excavated, and, as it were, towards the postero-lateral angles. The spines decidedly less 

 numerous, and the median sulcus more pronounced on both valves." 



The double area, so like that of some Orthis, is well displayed in this little shell ; but it 

 cannot be considered a character of generic value, as such likewise occurs 

 to a greater or lesser extent in many species of Spirifera, such as in 

 Sp. striata and Sp. alata, but more especially so in Sp. decora of 

 Phillips. Professor King and Mr. Howse are of opinion that Sp. 

 Sp. Clannyana, Clannyana should be generically separated from Spirifera proper, and 

 seen from the beaks, jj ave pl ace d. it in M'Coy's Martinia, a genus I have hitherto declined 



enlarged. / 



m. Area of ventral adopting, from its not appearing to be founded upon any important or 

 valve, d. Deitidium. va ] j^ internal character. I have therefore deemed it preferable to allow 



N. Area of dorsal . . . , . 



valve. the shell under description to remain (provisionally at least) under Spiri- 



1 These spines were first noticed by Baron Schauroth, in his ' Ein Beitrag zur des deutschen Zech- 

 steingebirges,' fig. 16, 1853, and afterwards in his ' Ein neuer Beitrag zur Palaeontologie,' 1856. Their 

 existence is now also admitted by Professor King, in his Notes on Permian Fossils (' Annals and Mag. of 

 Nat. Hist.,' March and April, 1856) ; and Mr. Howse informs me that he was in error when he stated in 

 his paper in the 'Annals' for 1847, that the surface does not appear to be covered with spines. 



2 ' History of British Animals,' p. 376, 1828 ; and Ure's ' History of Rutherglen,' pl.xiv,fig. 12, 1793. 



3 'Geol. Trans., 2d series, vol. v, pi. liv, fig. 8 ; and Phillips's 'Palaeozoic Fossils of Cornwall,' &c, 

 p. 69, pi. xxviii, fig. 119, 1841. 



