88 INTRODUCTION. 



originating under the platform, extends longitudinally and freely with a slight upward 

 curve to about a third of the length of the valve; to the inner extremities of the socket 

 ridges are affixed the spiral horizontal cones, with their extremities directed towards the 

 lateral margins of the shell; the crura appear to have been united before the lamellae 

 commence their spiral coils :^ no defined septum is visible along the bottom of the valve, 

 but a minute rudimentary mesial ridge which divides the quadruple impressions of the 

 adductor. 



In the larger or ventral valve the dental plates are more or less developed, exhibiting 

 on and close to their inner sides, impressions of the pedicle muscles; the adductor leaves, 

 a small oval scar separated by a minute mesial elevation under and outside of which are 

 seen two other larger impressions due to the cardinal muscles. 



Ohs, Under Athyris I have mentioned all my reasons for the limitation here in- 

 troduced, and shall therefore only add one or two other observations. Professor King 

 separated from his genus Cleiothpis, certain shells which at least for the present I should 

 wish either to include with Spirigera, or to place in a section of this last. The author 

 proposes for these the term Betzia, with the following diagnosis -. — " A Spiriferidia ; in 

 general oval long itud'mally^ ribbed or striated, loith large punctures ; larger valve foraminated 

 at or near the apex of the umbone, with a large triangular area, and a closed Jissure. 

 Type — T. Adrieni, De Verneuil ; T. Baglii, Salteri, and Bouchardii, Dav. T. Oliviani. 

 T. ferita, is likewise mentioned.^ I do not pretend that some of the shells here 

 mentioned may not require to be separated and formed into a small sub-sectional group, 

 but hitherto nothing has been seen or said regarding their interior ; and in consequence 

 its distinctive claims have not been sufficiently tested : much, indeed, has yet to be achieved 

 before a multitude of Palaeozoic species can be placed into their proper places, and which 

 time alone can accomplish. 



Geol. range. — The existence of this genus seems perhaps to have exceeded that of 

 Athyris ; appearing in the silurian epoch, it has continued up to the lower Lias, above which 

 no examples have been discovered. 



Examples: S. concentrica, V. Euch, sp. ; 8. pectinifera, J. Sow.; S. Boissgi, Def. ; 

 8. lamellosa, Def. ; plano-sulcata, Phil., sp. ; serpentina, Kon., sp. ; Hispanica, Ferrone- 

 sensis; Fsquerra, Vern. ; axiocolpos, Emmerich,^ &c. 



it always occurred. Professor King has figured the aperture in the hinge-plate of T. pectinifera, and I 

 doubt not, that with time it will be recognised in many other species. 



1 This character has been well figured by J. De Carle Sowerby in S. pectinifera. Min. Con. T. 616. 



2 A Monograph of English Permian Fossils, p. 137, 1849. 



^ This species occurs in the lower or black Lias of Koessen (Tyrol), and has been clearly investigated 

 by M. Suess, of Vienna, who kindly sent me his figures, and a description of this remarkable shell. 



