162 AMERICAN JOURNAL 



Panamensis., Unio MowelU, Sphcerium oneridionale, and 3Iyceto- 

 pus Weddelli ally the fauna specifically to that of tropical South 

 America, Helix griseola, Q-landina Dysoni, Succinea ivjiata, 

 Vaginulus Floridanus, Planorhis tumidus, Helicina tuherculata 

 and H. turhinata are more northern forms, which in Nicaragua 

 commingle with those of a more southern origin. Bulimiis zebra, 

 Achatina actona and Oyclotus translucidus are common to Cen- 

 tral America, South America and the Antilles ; Gruppya Gund- 

 lachi and Bulimus costato-striatus are Cuban species. The only 

 species common to Nicaragua and the neighboring State of 

 Gautemala are 3Iela7iia corvina, Bulimus zebra, Achatina octona, 

 Physa purpurostoma, Planorbis tumidus, Planorbis Kermatoides, 

 Oyclotus translucidus, Helicina rostrata, and H. merdigera. 

 Generically Tebennophorus is North American, Grlandina Cen- 

 tral American, whilst Mycetopus and Tornatellina are South 

 American, 



The land snails of Gautemala, Honduras, Yucatan and Mexico 

 resemble those of the West Indies in the prevalence of Oylin- 

 drella, Macroceramus, Adamsiella, 3Iegalomastoma, Qliondropo- 

 ma, Cistula, and Tudora, none of which genera have been ob- 

 served in Nicaragua and south to the Isthmus of Darien. This 

 circumstance, viewed in connection with the distribution of the 

 Nicaraguan species, points to a difi"erent origin for the fauna, 

 and I am thereby induced to regard Nicaragua as comprised 

 within the Columbian Region of the distribution of land shells, 

 and not within that of Mexico. 



