M. I. G. Saint-Hilaire on an American Bat. 233 



the even and rounded form of its stellae, this latter having the 

 laminae of its stellas " filamenteuses, acerees ou cuspidees." Lam. 

 Anim. sans vert, vol.'ii. p. 267. 



In consequence of these considerations, I have thought it con- 

 venient to constitute a newr genus for this Madrepore, and I pro- 

 pose to give it the appellation of Thamnasteria, which signifies 

 " a bush with close branches covered with stars." The following 

 are its characters : 



THAMNASTERIA. Polyparium petrosum, ramosum ; super- 

 ficies ramorum stellis lamellosis, sessilibus, obtecta ; lamellis 

 linearibus, rotundatis. 



And its specific characters will be 



Th. Lamourouxiiy (oss'ilis, ramosa, fasciculata, dilatationibus et 

 contractionibus circularibus, alternis ; stellis rotundis, subplanis. 



* jt* Upon this we have only to observe that the word ramosa ought not to 

 have been given in the specific character, as it was already placed in the 

 generic. — Ed. 



Art. XXX. 3Iemoir on an American Bat, a new Species 

 belonging to the genus N_yctinomus. B^ M. Isidore 

 Geoffroy Saint-Hilaire.* 



[Read before the Soci^te d'Histoire Naturelle, at Paris, March 5th, 1824.] 



There exists an opinion regarded as paradoxical by many 

 naturalists, but which to others seems to bear the character of 

 truth, and therefore to be very important, namely, that the ani- 

 mals of one continent belong to it exclusively and are never met 

 with in the other. To appreciate the value of this opinion, ac- 

 curately, we must necessarily make this distinction : — is it meant 

 to be asserted, that animals of either of the two worlds cannot 

 be united as species of the same genus with those of the other, 

 or, is it merely pretended that the animals of the two worlds are 

 specifically diff'erent ? 



* Translated from the Annahs des Sciences Natur dies, for April, 1824. 



Vol. 1. Q 



