48 INTRODUCTION. 



Or<?er— SARCICOBRACHIA. 



1. Fam. LiNGULiDJE. Genus Lingula. 



2. .. Obolid^. G. Oholus. 

 Craniad^. G. Crania, Siphonotreta, Criopus. 

 DisciNiD^. G. Biscina, Orbiculoidea, Trematis. 

 CALCEOLiDiE. G. Calceoltt. 

 Davidsonid^. G. Bavidsonia. 

 Productid^. G. Productus, Strophalosia. 

 SiROPHOMENiDiE. G, Stropkomena, Leptcsna, Chonetes, Orthis, Streptorhynchus, 



Orthisina, Bicalosia, Platystropliia. 



Orrfe?— SCLEROBRACHIA. 



9, Fam. Hypothyrid^. G. Isorhynchus, Hypothyris, Camarophoria, Uncites, Pen- 

 tamerus. 



10. „ Spiriferid^. G. Atrypa, Athyris, Cleiothyris, Betzia, BeUhyris,Triyonotrefa, 



Spirifer, Martinia. 



Orrfer— ANCYLOBRACHIA. 



11. Fam. Strigocephalid^. G. Strinyocephahs. 



12. „ Terebratulid^. G. Epithyris, Terebratella, Terebratula, Pyyope, Eudesia, 



Meyerlia, Waldheimia. 



13. „ RHYNCHORiDiE. G. Ismenia, BelthyridcBa, RhyncJiora. 

 14 „ Magasid^. G. Mayas, Bouchardia. 



15. „ THECiDvEiDiE. G. Thecidaa. ' 



16. „ ARGiopiDiE. G. Aryiope. 



The chief objection to Professor King's arrangement lies in the sometimes great 

 sub- division of the genera, and to which we will revert hereafter when treating the respective 

 sections.' 



Since the last-named publication two other schemes have been introduced by Dr. Van 

 der Hoeven^ and Professor Quenstedt.^ The first of those authors admits of eight genera : — 



^ I take this occasion to express my warmest thanks to Professor King for the friendly and unreserved 

 manner in which he has communicated to me his views, and for the liberal loan of all the specimens 

 belonging to his collection, now forming part of the Museum of the Queen's College, Galway ; and I hope that 

 any difference of opinion I may have expressed, will be considered as having only been dictated by a 

 desire similar to his own, viz., the advancement of science. I am happy to repeat the same, relative to 

 Professor M'Coy. 



2 Handbuch der Zoologie, 1850. ^ Handbuch der Petrefactunde, 1851. 



