THE NAUTILUS. 1 



Margaritana sinuata. but I see no reason, why there should not exist 

 species of Margaritana with hinge teeth, in fact, this is a logical 

 postulate, if Margaritana in general is a primitive genus. Similar 

 cases of genera containing species both with and without lateral teeth 

 are met with, for instance, in Alasmidonta and Symphynota. Thus 

 Pseudunio is to be regarded as a pure synonym of Margaritana, and 

 has nothing whatever to do with Unio. Of course, the gill structure 

 is yet unknown, but we have every reason to expect, that it will 

 prove to be like that of Margaritana margaritifera, or will be very 

 close to it. 

 Family Unionid^ d'Orbigny (restr.) 



This family has the following characters. The gill-diaphragm is 

 complete; there is a tendency to approach the mantle margins at the 

 point where the gill diaphragm reaches the mantle margins, and a 

 tendency to unite these margins above the anal opening, so as to 

 form an incomplete anal siphon, and leave, above it, a supraanal 

 opening (This tendency is absent in a few North American types). 

 The gills always have well-defined septa running parallel to the 

 filaments, thus forming more or less regular watei'-tubes. In the 

 female, in the marsupial gills, these water-tubes become ovisacs, and 

 are much narrower than they are in the non-marsupial gills of either 

 sex. The marsupium is formed either by all four gills, or only by 

 the outer gills, or parts of the latter. The glochidium has various 

 shapes, with or without hooks. 



(7b be co?ichtded.) 



BOSTON MALACOLOGICAL CLUB. 



The Boston Malacological Club has just closed a most interesting 

 season of meetings. "With a membership of about thirty, the attend- 

 ance has averaged twenty or more. It has been a matter of surprise 

 to the members to see the diversity of subjects well handled by the 

 different speakers. An idea can be had from the following as ex- 

 amples. Dr. Paul Bartsch on Collecting in the Philippines; Mr. F. 

 N. Balch on Nudibranchs ; Mr. C. W. Johnson on Distribution and 

 variation of Busycon and Melongena ; Mr. D. L. Beldingon Economic 

 forms in Mass.; Mr. Arthur Way on The Life of Say. Prof. Morse 

 on Eyes in Lamellibranchs and other topics ; Mr. Winkley on 

 Mollusca and Changed Climate. We have also had exhibited in- 

 teresting letters, photographs, drawings and specimens. 



Henrt "^ "^ ;t, Sec. 



