248 



CHAPTER XIV * 



CARBONIFEROUS LIMESTONE BRACHIOPODA. 



Discina bulla (M'Coy). 



Desc. Hemisplieroidal, regularly tumid, inflated ; base circular ; 

 antero-posterior profile nearly semicircular ; greatest depth 

 not at the apex, but at about the middle of the length. Sur- 

 face glossy, smooth, or with very faint, obsolete, obtuse, con- 

 centric and longitudinal striae; a small sulcus extends ante- 

 riorly a short way from the apex, which is obtuse, and nearly 

 vertically over the posterior margin. Length 7^ lines, width 

 the same, proportional depth -f-^-^, distance of apex from pos- 

 terior margin -^^q. 



The remarkably inflated bubble-like form of this species easily 

 separates it from any I know. The beak is very little within the 

 margin. The traces of concentric markings are rather broad and 

 very obtuse lines, scarcely recognizable in the only specimen 

 which has occurred ; the traces of very fine longitudinal striae 

 are only to be seen on one decorticated spot with a lens, the 

 general aspect of the specimen being remarkably smooth. 



Reddish sandy bed of limestone at Lowick, Northumberland. 



{CoL University of Cambridge.) 



Seminula ficus (M'Coy). 



Desc. Longitudinally broad- ovate, gibbous; greatest width 

 slightly in front of the middle j lateral margins slightly raised 

 into a tri-undate, wide, flattened wave, towards the entering 

 valve in old specimens (lines of growth indicating a regular 

 margin up to I inch long) ; no distinct ridge extends from 

 this wave towards the beak of the entering valve, but the sur- 

 face near the front slopes more rapidly away from it towards 

 the lateral edges ; on the receiving valve obscure indications 

 of the mesial hollow and bounding ridges extend a short way 

 towards the beak in specimens an inch and a half long; re- 

 ceiving valve evenly tumid, regularly arched from the beak to 

 the front margin ; greatest depth about the middle ; beak mo- 



* The species in this chapter date from the 'Annals ' for Dec. 1852. 



