NO. 1863. MOLLUSKS OF THE GENUS ALVANIA—BART8CH. 335 



Sutures not channeled. 



Sutures strongly constricted. 



Spiral cords between the sutures on the penulti- 

 mate whorl, 12 filosa, p. 342. 



Spiral cords between the sutures on the penulti- 

 mate whorl, 5 alaskana, p. 343. 



Spiral cords between the sutures on the penulti- 

 mate whorl, 4. montereyensis, p. 343. 



Spiral cords between the sutiu-es on the penulti- 

 mate whorl, 3 excurvala, p. 344. 



* Sutures not strongly constricted. 



Spiral cords between the sutures more than 10 

 on the last whorl. 



Shell ovate profundicola, p. 345. 



Shell elongate-conic. hoodensis, -p. 345. 



Spiral cords between the sutures less than 7 on 

 the last whorl. 



Shell elongate-conic electrina, p. 346. 



Shell ovate. 



Base with 4 spiral cords pcrlata, p. 347. 



Base with more than 4 spiral cords. 

 Spiral cords between the sutures, 4. 

 Axial ribs on the last whorl, 



20. -• galapagensis, p. 347. 



Axial" ribs on the last whorl, 



14 nemo, p. 348. 



Spiral cords between the sutures 

 more than 4. 



Body whorl inflated. 



WTiorls strongly rounded. roscTTZfl, p. 349. 

 'WTiorls almost flattened, .fossilis, p. 349. 

 Body whorl not inflated. 



Axial ribs on last whorl 



about 45 iliuliukensis, p. 350. 



Axial ribs on last whorl 



about 30 compacta, p. 351. 



Axial ribs on last whorl 



about 20 acutilirata, p. 352. 



Junction of axial ribs and spiral cords nodulose. 

 Sutures channeled. 



Spiral cords between the sutures, 2. 



Basal cords, 3 cosmia, p. 352. 



Basal cords, 4 purpurea, p. 353. 



Spiral cords between the sutures more than 2. 

 Spiral cords between tlie sutures, 3. 



Cord at the summit equal to the other two in 



strength halia, p. 354. 



Cord at the summit not equal to the other two 



in strength ima, p. 355. 



Spiral cords between the sutures more than 3. 

 Spiral cords between the sutures, 6, or more. 



Spiral cords between the sutures equal clarion ensis, p. 356. 



Spiral cords between the sutures unequal. Zara, p. 357. 



