104 THE NAUTILUS. 



SOME NOTES ON THE HINGE OF THE SPIIAERIIDAE 



BY V. STERKI 



The configuration of the hinge of the Sphgeriidge has at- 

 tracted the attention of malacologists for a long time, and 

 there has been a good deal of discussion about some of the 

 features. It appears that a few points are still open to con- 

 troversy, and some may have been overlooked. The notes 

 following contain part of the results of examining many 

 thousands of specimens during the last thirty years. Special 

 attention has been paid to the primitive formation of the 

 hinges in the early nepionic stages of these mussels, with the 

 subsequent changes to maturity, and to the particularly in- 

 teresting subject of variation, with respect to the classifica- 

 tion and the standing of species. This last topic, however, 

 can be only summarily sketched here, and will have to be 

 considered in a special article. 



General Configuration. - - In all of the Sphasriidse now 

 known, principally the genera Pisidium, Splicsrium, Muscu- 

 lium and Eupera, the hinge is uniform so far as essential 

 features are concerned. It is much of the same configuration 

 as that of the Cyre/nidcc, yet with some significant differences, 

 especially in the cardinals, and there are probably some dif- 

 ferences in the soft parts. On the other hand, this hinge is 

 markedly different from that of the Naiades, not only by the 

 presence of all '"teeth" in all species, but also by the fact 

 that there is no such embryonic larval stage as the glochidium 

 and lasidium. 



Of teeth, there are the CARDINALS at the center, in front of 

 the ligament, one in the right valve and two in the left, and 

 the LAMINAE, two anterior and two posterior in the right and 

 one of each in the left valve. The term "lateral teeth," for 

 the same, is not only cumbersome but inadequate, inaugurated 

 at a time when the parts of the mussel, i. e. the animal, were 

 misunderstood. The term "lamina?" appears to be prefer- 



