50 



THE NAUTILUS. 



glochidia. In assigning an age to these shells it is quite sure 

 that the tetralasmus discharges its glochidia in March and early 

 April, so that when picked up on May 25, these shells were just 

 about fourteen months old, from the date of discharge from their 

 mother's gills. 



In the case of the texasensis (which spawns somewhat later) 

 it is possible that these were dropped by fish of which, at least 

 six species) obtained access to the pit on May 7, 1916 (on 

 which date an overflow occurred), thus making about thirteen 

 months. At any rate the maximum age of either species is 

 fourteen months from their mother's ovisacs. One of the U. 

 tetralasmus is shown of natural size in PL VII, fig. 4. 



Another observation concerning pond mussels might here 

 prove of interest. A large pond was cut into two by a railroad 

 enbankment, a culvert preserving the level and providing com- 

 munication between the two. In the lower and larger pond a 

 half-bushel of Yonkapin (Nelumbium hiteum) seed was sown. It 

 was six years before these seed germinated. These plants, dur- 

 ing the summer, cover the entire surface of the pond with their 

 broad peltate leaves. In this pond the writer planted a colony 

 of a dozen Anodonta grandis. Several years after, taking ad- 

 vantage of extreme low water, the writer made a careful survey 

 of the?e twin ponds, with the result that hundreds of Anodons 

 could be found in the upper pond, but not a single one was 

 found in the lower pond. Either the shade killed the young 

 shells, or else the glochidia-laden fish avoided the shade of the 

 lotus plants and congregated in the upper pond (there are no 

 Nelumbii in the upper pond). Is not this avoidance of shade 

 a reason for the paucity of unios in the tropics ? 



A NEW SOUTH AFRICAN NESOPUPA. 



BY H. A. PILSBRY. 



Nesopupa farquhari, n. sp. 



Among Pupillidae sent by Mr. J. Farquhar there is a new 

 species from Grahamstown which may be defined by comparison 



