2G0 NOTES ON THE TERMIAN SYSTEM OF 



in the Table. It is also stated in the " Perm. Mon." to occur in 

 the compact-limestone at Whitley and Tynemouth. 



l-t. LIMA, Bnujn'itre. 



1. L. Permiana, King. 



Though I had taken single valves of this shell many years ago, 

 yet the slight distinguishing characters it presented have always 

 prevented me from considering it distinct from the preceding. 

 But Mr. Kirby has, with his usual success, obtained such a fine 

 series of it from the places mentioned in the Table, that its ad- 

 mission into the fauna can be no longer objected to. It has 

 also been discovered by Baron Schauroth at Poessneck; and 

 some examples kindly sent me for comjoarison agree with ours in 

 every particular. 



It differs from the preceding chiefly in the obliquity of the 

 valves, in the narrowness of the hinge-line, and the more tri- 

 angular appearance of the area. It has also no byssal notch. 

 The surface, in perfect specimens, is ornamented with fine par- 

 allel lines of growth, and small radiate depressions run from the 

 umbones to the margin. For the present, it may be left in the 

 genus Lima., but this requires further examination. 



In the shell-limestone of Tunstall and other localities; not 

 very common. 



15. MONOTIS, Brown. 

 1. M. SPELUNCARIA, Schlotll. 



Certainly no one at all conversant with this pre-eminently 

 characteristic Permian bivalve, can assent to its being unneces- 

 sarily broken up into three species, as proposed by the author of 

 the " Perm. Mon." 



As pointed out in the " Tyneside Catalogue," the convex 

 valve when perfect exhibits " a few strong imbricated or granu- 

 lated diverging ribs, between which there are others much finer 

 and closer together." The granulations are strongest on one 

 side of the valve, and occur only on those specimens that are of 

 very regular growth. On the coarser and larger individuals the 

 ribs are covered with strong imbricating processes, which are 



