64 



THE NAUTILUS. 



Anatomy. 



Stipraanal opening probably separated from the anal by a 

 short mantle-connection, but in all my specimens this is torn 

 by rough handling. Inner lamina of inner gills free from ab- 

 dominal sac. All four gills marsupial in the female. Placentae 

 well developed and sub cylindrical. 



Anal opening with small papillae, branchial opening with 

 well developed papillae. Palpi as usual, their posterior margins 

 connected for about one third of their length or less. 



As to the color of the soft parts, which is so characteristic in 

 barnesiana, not much can be said, since my material has been 

 too long in alcohol. But in most of my specimens the gills are 

 yet distinctly suffused with black. The placentae have been 

 rendered whitish, but here and there traces of a dark stain are 

 preserved (which is disappearing gradually). It is quite pos- 

 sible that the color of the placentae originally was similar to 

 that of barnesiana. 



The glochidia are subelliptical, slightly higher than long; L. 

 0. 15, B. 0. 18, thus agreeing with those of F. barnesiana. 



NOTE ON THE RELATION OF SNAIL FAUNA TO FLOODS. 



BY A. RICHARDS. 



During the years 1911 to 1916, while the writer was a mem- 

 ber of the faculty of the University of Texas, a series of inci- 

 dental observations on 'the snail fauna of Waller Creek was 

 made. These observations have now come to an end due to the 

 change of residence of the observer. It seems not unwise, 

 therefore, to publish a short note on the subject in the hope 

 that the facts recorded, although fragmentary, may have a 

 bearing on the work of some other follower of snail life. 



Waller Creek is a small stream near the University of Texas 

 at Austin. It is some four miles in length and empties into 

 the Colorado River at a distance of perhaps two miles below the 

 University. That portion of the stream close to the University 

 between Fifteenth and Twenty-seventh Streets, was most closely 

 observed, but data was also collected from the region below. 



