THE NAUTILUS. 83 



1 have run over the literature and manuals and have not found 

 any reference to viviparity in Corbicula or Gyrena, though of course 

 it is well known in the allied Sphceruim and Pisidium. If it is a 

 characteristic of the Old World Corhiculas, it is singular that it has 

 not been hitherto noted. 



The prodissoconch in these young shells is rounded, polished and 

 translueent, and presents no remarkable peculiarities. 



If the brooding of the nepionic young in a marsupial sac is a fur- 

 ther point of distinction between the New and Old World forms, it 

 is probable that it may be regarded as raising the value of the sub- 

 division to higher than sectional rank. 



'PYEAMIDULA" ELRODI AND EPIPHRAGMOPHORA CIRCUMCARINATA. 



BY ROBERT E. C. STEARNS. 



In connection with my remarks upon the above-named forms in 

 the October number of The Nautilus, and Dr. Pilsbry's com- 

 ments that follow, he says : " The difference between Dr. Stearns' 

 views and my own, of the affinities of the two Helices, may be due 

 to his having, perhaps, no examples of circiimcarinata at hand for 

 direct comparison with elrodi." This suggestion is correct. I have 

 not seen an example of ciraoncarinata for ten years, and only a 

 single specimen of Elrodi, that heretofore referred to by me. 



The dominant features of these shells are surprisingly alike. The 

 many though less conspicuous characters indicated by Tk'. Pilsbry in 

 their bearing on the distinctive point, must therefore be accepted. 

 The remarkable similarity exhibited between the forms in question 

 are presumptively, as Dr. Pilsbry observes, the result of similar envi- 

 ronmental conditions " acting upon organisms originally diverse, and 

 indeed not closely related." 



Closeness of relationship or otherwise, among land-snails inhabit- 

 ing the same geographic or physiographic area, though the area may 

 include a broad extent of territory, is another and very interesting 

 question. 



Regarding the relations of the strigosa group of snails, I have for 

 a long time held the opinion that it was decidedly out of place in 



