THE NAUTILUS. 129 



tracum, more or less incrusteel with iron oxide, and sculptured only 

 by feeble incremental lines. Beaks inconspicuous, binge as in the 

 genus, bearing two very small diverging cardinals in one valve with 

 a rather strong resilium between them which seems to carry a small 

 lithodesma; opposite valve edentulous; pallial line entire; inner 

 margins of the valves simple. Length 4.5 ; height 2.5 ; max. diam- 

 eter 1.3 mm. 



This species is proportionately much more elongate than any of 

 the other Pacific coast species and can be recognized at once by its 

 form. All of the others are more or less conspicuously equilateral, 

 and nearly all are larger. 



Habitat : with the preceding. The species is named in honor of 

 its discoverer. Only one specimen of this and the preceding species 

 has been seen. The present specimen within the valves had a large 

 number of minute smooth larval bivalves, but whether they belong 

 to the same species is uncertain, since the specimen did not contain 

 any of the fleshy portions of the animal. 



NOTES ON ANODONTA COUPERIANA AND A. GIBBOSA. 



BY L. S. FRIEUSON. 



In the " Synopis of the Naiades" of Mr. C. T. Simpson (1900), 

 it is stated that the Anodonta couperiana Lea (with its variety A. 

 dunlapiami), is a synonym of the Anodonta gibbosa Say. In this 

 statement Mr. Simpson is followed by nearly all students who have 

 handled the subject, rendering a difficult study still more confused. 

 These species are quite distinct and belong to separate groups, and 

 even possibly to different genera. 



Anodonta couperiana is a fairly common species in most collec- 

 tions of any size. It is a handsome shell, with a bright, shining 

 epidermis, and I am informed by Mr. T. Van Hyning that it very 

 seldom cracks as other Anodontas are so prone to do. Its umbones 

 are like those of Anodonta inibecHlis Say, i. e., they hardly rise above 

 the hinge line. The corrugations are similar to the imbecilHs, and 

 some specimens verge towards the Ano suborbiculata of ^ay, which, 

 despite its large size and different shape, belongs to the same group. 



