372 



Mr. T. Davidson on the Classification 



calcareous lamellae differently disposed : the lower pair are riband- 

 shaped^ attached first to the crural base. They direct themselves 

 by a gentle curve to near the anterior portion of the septum, to 

 the sides of which they are affixed : the second pair arise on 

 either side of the upper edge of the septum, extending in the 

 form of two triangular-shaped lamellae. 



No true recent Magas has been discovered ; but some forms, 

 placed for the present in Terehratella, such as T. Cumingiij possess 

 characters of this genus. 



Subgenus Waltonia. 



Apophysary system consisting of a pair of riband-shaped 

 lamellse fixed to the crural base and to an elevated plate. 



41. Waltonia Valenciennii, Dav. 1850, Ann. and Mag. of Nat. 

 Hist. vol. V. pi. 15. fig. 1. 

 Hab. New Zealand. 



VIII. Genus Bouchardia, Dav. 1849. 



Apophysary system anchor-shaped, consisting of an elevated 

 central plate, to which are affixed two short lamellse. 



42. Bouchardia rosea, Humphrey sp. ; Dav. Bull. Soc. Geol. de 

 France, vol. vii. 2nd ser. pi. 1. fig. 1-6, 1849. 



Hab. Rio in 13 fathoms. 



Obs. Magas, Waltonia, and Bouchardia are related to Tere- 

 bratella by such species as Terebratella crenulata, Evansii and 

 Cumingii. 



IX. Genus Argiope, Deslongchamps, 1842. 

 Megathyris, D'Orb. 1847. 



In the imperforated valve one or more prominent septa ; apo- 

 physary system consists of a distinct loop, originating at the 

 base of the dental sockets and furnished with converging crural 



