208 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 2 



Holotype: No. 734 (Calif. Acad. Sci. Paleo. Type Coll.), dredged 

 in from 3 to 9 fms. in Bahia Honda, Panama. L. G. Hertlein collector. 

 Twenty-five additional specimens were dredged at the same locality 

 and 1 specimen collected on the rocks at Panama City. 



In the key to the west coast species of the subgenus Miralda given 

 by Dall and Bartsch,^^ Odostomia azteca would follow armata which 

 was described from Mazatlan, Mexico, by Carpenter. It differs from 

 that species in the smaller size, and in having the upper spiral row of 

 nodules only slightly wider than the lower. These 2 species, together 

 with Odostomia aepynota Dall and Bartsch from southern and Lower 

 California, Odosto7?2ia terebellum C. B. Adams from Panama, and 

 Odostomia galapagensis Dall and Bartsch from the Galapagos Islands, 

 form a closely related group, the species of which differ only in the 

 details of the sculpture. Some of them eventually may be found to 

 intergrade through specimens from intermediate localities. 



Odostomia (Evalea?) isthmica Strong & Hertlein, new species 



Plate 19, Fig. 12 



Shell elongate-conic, milk white, polished, shining; nuclear whorls 

 almost completely immersed in the first postnuclear whorl, giving the 

 apex a truncated appearance; postnuclear whorls 8, slightly rounded, 

 narrowly tabulated at the summit, sharply contracted at the base, form- 

 ing a deeply channeled suture; periphery of the last whorl angulated, 

 with a faint raised thread on the angle (this thread is very faint on 

 the type but quite noticeable on some of the paratypes) ; base short, 

 well rounded, narrowly umbilicated ; entire surface of spire and type 

 marked with curved lines of growth and very fine, microscopic spiral 

 striations; aperture oval, outer lip thin, decidedly drawn forward in 

 the middle; columella slender, curved with a fold at its insertion. The 

 type measures: length, 3.2 mm; diameter, 1.5 mm. 



Holotype: No. 736 (Calif. Acad. Sci. Paleo. Type Coll.), dredged 

 in from 3 to 9 fms. in Bahia Honda, Panama. L. G. Hertlein collector. 

 Fourteen additional specimens were dredged at the same locality, and 

 17 specimens were dredged off Taboga Island, Panama. 



This species would require a separate subdivision if placed in the 

 key to the west coast species in the subgenus Evalea. In many ways it 

 resembles some species of the genus Pyramidella but has only the single 



41 Dall, W. H., and Bartsch, P., U. S. Nat. Mus., Bull. 68, 1909, p. 176. 



