WEST AMRHICA^' I'YKAMlDKI.I-l I' 



M(^LLI'HKS. 41 



Spiral Htriatioiis extending uniforn.ly over the axial ril.s an-l intercostal spaces be- 

 tween the sutin-es— C'ontinned. 



Intercostal spaces terminating posterior to tlie periphery, having a plain, smooth 

 hand in the sntun— Continued. 



Intercostal spaces n;)t pinched in at the summit— Continued. 

 Axial rilis moderately protract! v( — Continued. 

 Whorls not overhanging. 



Intercostal spaces 4 times as wide as the rih^.... mexicana, p. 45. 

 Intercostal spaces less than 3 times as wide as the ribs. 

 All post-nuclear whorls well rounded. 



Axial ribs poorly developed attrita, p. 4(). 



Axial ribs well developed. 



Spiral striations strong vichohi, p. 4(5. 



Spiral striations microscopic. 



Axial ribs 16-22 lorquata, p. 47. 



Axial ribs 16-28 s/i//ma, p. 48. 



Early post-nuclear whorls well rounded, later ones flat- 

 tened * '•"^^'^■^'' P- '^^• 



Axial ribs vertical or nearly so. 



Axial ribs much enfeebled on the last whorl car-penteri. p. 49. 



Axial ribs strong upon all the whorls. 



Axial ribs 16 simpsoni, p. 49. 



Axial ribs 16-22 profimdkoJa, p. 50. 



Intercostal spaces extending to the suture. 



Shell very robust galinnoi, p. 51. 



Shell not robust. 



Shell broadly conic. 



Shell large, length 6 mm humerosa, p. 52. 



Shell small, length less than 4 mm c—h—adamsi, p. 52. 



Shell slender. 



Axial ribs extending over the base ■'<erra>, p. 53. 



Axial ribs not extending over the base. 



Axial ribs 14-21 "''esto, P- 54. 



Axial ribs 14-16 pazana, p. 54. 



Spiral striations confined to the intercostal spaces between the sutures. 



Spiral striations only two between the sutures gaJapagemi,, p. 55. 



Spiral striations more than two between the sutures. 



Intercostal spaces uniformly spirally striated vndata, p. 55. 



Intercostal spaces not uniformly spirally striated. 



Intercostal spaces marked by a peripheral line of j^ts and numerous 

 striations. 



Intercostal spaces less wide than the ribs ajfims, p. 56. 



Intercostal spaces wider than the ribs. 



Spiral striations between the sutures 16 phanea, p. 56. 



Spiral striations between the sutures 24 impel ialis, p. 57. 



Intercostal spaces marked by a peripheral and a submedian line of pits 

 and numerous fine striations. 



Fine striations between median pits and summit 40. .smithsom, p. 57. 

 Fine striations between median pits and summit 20. . .gracilior, p. 58. 



