WEST AMERICAN PYRAMIDELLID MOLLUSKS. 231 



Subgenus HEIDA Ball and Bartsch. 

 Heida Dall and Bartsch, Proc. Biol. Soc. Wash., vol. 17, 1904, p. 13. 



Shell without axial or spiral sculpture beyond mere lines of growth 

 and exceedingly fine spiral striations ; peritreme continuous, aperture 

 rissoid. 



Type. — Syrnola caloosaensis Dall. 



ODOSTOMIA (HEIDA) PANAMENSIS Clessin. 

 Plate 30, fig. 6. 



Odostomia panamensis Clessin, Mart. Chem. Conch. Cab., 2d ed., Pyramidellidse, 

 1900, p. 120, pi. 28, fig. 9. Odostomia (Heida) pahamcnsis (Clessin) Dall 

 and Bartsch, Proc. U. S. Nat. Mus., vol. 30, 1906, pp. 365, 366, pi. 2G, fig. 4. 



Shell small, heavy, elongate-ovate, whorls increasing regularly in 

 size, milk white, sliining. Nuclear whorls small, almost completely 

 obliquely immersed in the first of the succeeding volutions. Post- 

 nuclear whorls moderately and evenly rounded, of porcellanous tex- 

 ture, without any apparent marking, separated by a well marked 

 suture. Periphery of the last whorl full and rounded. Base inflated, 

 well rounded. Aperture small, decidedly rissoid, almost channeled 

 anteriorly, posterior angle acute; outer lip decidedly curved back- 

 ward anteriorly, very tliick within but beveled to form a sharp edge; 

 columella extremely short, somewhat reflected, and connected pos- 

 teriorly with the very strong parietal callus, wliich is fully as tliick as 

 the edge of the outer lip and connects with it at the posterior angle of 

 the aperture, thus forming a complete peristome. A prominent 

 oblique fold is present on and a little anterior to the insertion of the 

 columella. 



There are two specimens of this species in the Berlin collection from 

 Panama. We have considered the best preserved individual, which 

 evidently served Clessin for his description and figure as liis type, and 

 have here rediagnosed and figured it. It has six post-nuclear whorls 

 and measures: Length .3.1 mm., diameter 1.5 miti. 



Clessin for some unaccountable reason changed the characters of the 

 aperture in the above-cited figure to harmonize with the typical 

 Odostomia aperture. He seems to have failed entirely in recognizing 

 the pecuharities of the present species. 



0. (Heida) iMnamensis Clessin, represents the first member of this 

 subgenus on the west coast of America; several additional species 

 inhabit the southeast coast. 



Subgenus ODOSTOMIA s. s. 



Odostomia Fleming, Edinburgh Encyc, vol. 7, pt. 1, 1817, p. 76. =Odontostomia 

 Jeffreys, Mai. and Conch. Mag., 1839, p. 34, same type. = Turritostomia 

 Sacco, I Moll, del Piemonte e della Liguria, 1892, p. 41, same type. 



