MONOCONDYLCEA. 



45 



V. SUBGENUS MONOCONDYLCEA. 



q" 





H 





k1 









B 





125 





c: 





CJ 





O 





fc 





c 



a 





. 



14 







O 





fc 





tH 





w 





ft 





- 





(H 





■J. 





y, 











2 





SUBROTUND. 



*Franciscana. Moricand. 



OBOVATE. 



*Paraguayana. D' Orb. 

 *Parchappii. D' Orb. Schom. 

 *Corrientesensis. D 'Orb. 

 *Guarayana. If Orb. 



M 





H 





Kl 





i* 





O 





» 





O 





O 





O 





Is 











S 









H 



O 



H 





O 





fc 





>H 





w 





ft 





s 





!* 





CO 





fc 





O 





!2i 



I 



OBOVATE. 



*fossiculifera. Z>' Orb. 



*Vondenbuschiana. Lea. 

 Margari. Zollingeri. Mousson. 2 

 Margari. crispata. Mousson. 

 Margari. fragilis. Mousson. 



Minuana. If Orb. 



1 D'Orbigny, the distinguished traveller in South America, forms the genus Monocondylaea for a group of 

 shells which he has first observed, and which possess a single cardinal tooth and no lamellar tooth. This tooth cer- 

 tainly diifers from that of the Margaritanafluviatilis, Schum., Alasmodonta, Say. I am indebted to the great kind- 

 ness of M. D'Orbigny for the first five- — -the sixth one I place here with some hesitation, as to its proper situation, 

 never having seen it. The shell figured by Spix, PI. 25, Figs. 1 and 2, under the name of Aplodon inerme, but f 

 not described in the text, evidently belongs to D'Orbigny's genus Monocondyloea. It is certainly a most interest- 

 ing group, and it is to be regretted that we have no description of the animal. 



2 Menke and Pfeif, in Zeits. fur Maldk., say that these three shells are the same as Margaritana Vonden- 

 buschiana, Lea. 



12 



