324 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY, 
'Trivia panamensis Darr. 
Plate 12, figures 7, 9, 12. 
Trivia panamensis Dall, Nautilus, Aug., 1902, 16, p. 43. 
Dredged in Panama Bay with 7. atomaria. U. S. N. Mus. 109,205. 
ERATO Risso. 
Erato oligostata DALL. 
Plate 11, figure 8. 
Erato oligostata Dall, Nautilus, Aug., 1902, 16, p. 44. 
This is one of the smallest, if not actually the very smallest, of the genus. 
It was dredged in Panama Bay in 1888, with the two preceding species. U. S. N. 
Mus. 109,907. 
Trichotropidae. 
CERITHIODERMA CONRAD. 
Cerithioderma Conrad, Journ, Acad. Nat. Sci. Phila., March, 1860, 2d ser., 4, p. 295; 
type, C. prima Conrad, op. cit., pl. 47, fig. 30; Dall, Trans. Wagner Inst» 
1892, 3, p. 202; Harris, Bull. Amer. Pal., 1895, 1, p. 15, pl. 1, fig. 10. Eocene 
of Alabama. 
Mesostoma Deshayes, An. s. Vert. bas. Paris, 1861, 2, p. 416; 1st sp. M. pulchra 
Deshayes, op. cit., pl. 28, figs. 13-16. Parisian Eocene. 
Cerithioderma pacifica Darr, n. sp. 
Shell small, thin, pale olivaceous, with a. thin, fibrous, adherent periostracum 
and about five whorls exclusive of the (lost) nucleus; suture distinct, somewhat 
constricted, not appressed ; whorls well rounded, on the fourth with about sixteen 
slender low ribs extending vertically from suture to suture, and crossed by tw 
prominent spiral ridges of about the same strength as the ribs, the anterior ridge 
at the periphery ; on a third similar ridge bordering the base the suture is laid and 
the ribs cease ; on the base are four spiral ridges, low and rounded, subequal with 
subequal interspaces, but the region of the canal is not sculptured; in the adult 
this sculpture is obsolete on the last whorl, and, on the spire, the intersections are 
sometimes nodulous; aperture wide, ovate, the outer lip thin, simple, the body 
with a faint callus; pillar short, twisted, straight; canal represented by a shallow 
hardly perceptible indentation. Lon. of defective adult, 11 +; of spire, four whorls, 
7; max. diam, 7 mm. 
