THE NAUTILUS. 53 



cestral home, but it is more probable that it will find some con- 

 ditions different. Environment will not make a change to suit 

 the mollusk and hence if its residence is not to its liking the 

 naiad will have to adapt itself to the residence or else retire 

 from the field. 



Then, too, there is a possibility that the two species will 

 hybridize and produce one or more other forms or races. Hy- 

 bridizing might wipe out either cariosa or coJiongoronta, or it 

 might wipe out both of them, replacing them by a race of mixed 

 blood. Bearing a resemblance to each other close enough to 

 suggest a common ancestry or a converging development and 

 living now side by side in the same spot, it seems to the writer 

 that a crossing of the two species will be not only possible but 

 highly probable. Indeed, one of the specimens of cohongoronta 

 collected in that spot may be a hybrid. Its anterior portion 

 has the glossy, peculiar straw-colored periostracum of cariosa, 

 while the other features of the shell are distinctly those of 

 cohongoronta. It will be interesting and profitable to note the 

 future history of the two species in this vicinity, especially as 

 the specimens of cohongoronta in the U. S. National Museum 

 (Cat. Nos. 219057 and 219058) will show the characters of the 

 shell at the time of its first arrival and form a basis of compari- 

 son with the shells of future generations. The specimens of 

 cariosa collected at the same time and place form catalogue 

 number 219059. 



THE STATUS OF LOBOA BRUNOI VON IHERING. 



BY PAUL BARTSCH. 



In the "Nautilus" for February, 1917, vol. 30, on pi. 4, fig. 

 7, and in the number for March, 1917, pp. 121-122, Dr. H. 

 von Ihering describes a new genus and species of landshell 

 from the Island of Trinidad, as Loboa brunoi. 



During a recent visit to Washington, Dr. Carlos Moreira, of 

 Brazil, submitted a shell to me for determination. This speci- 

 men, which is in a subfossil state, also came from the Island 



