388 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXXIV. 
Genus THATS Link. 
THAIS TRANCOSANA, new species. 
Plate XXXVI, fig. 3. 
Description.—Shell attaining a length of 26 mm., subovate, a little 
longer than wide, very thick, heavy; spire elevated; apex acute; 
whorls 4 or more, very slightly convex, increasing rapidly in size from 
apex downward; surface smooth except for an obsolete sculpture of 
3 or 4 revolving lines; body whorl much larger and more convex 
than others, regularly rounded, its surface ornamented by about 13 
obsolete revolving ridges. Aperture elongate-elliptical; outer lip 
thickened and dentate internally, four teeth visible in the type; back. 
of each tooth an internal revolving line; inner lip broad and smooth; 
canal short, narrow and oblique. 
Dien or decolleté type, length (restored), 27 mm.; lati-. 
tude, 19 mm.; length body whorl, 21 mm.; length aperture and canal, 
16 mm.; latitude aperture, 5 mm. 3 
Notes.—The type exhibits a broad sinus or groove in the inner lip 
beginning at the middle and extending to the posterior extremity of 
the aperture. Doctor Dall suggests that the groove may have been 
worn in the lip -by a hermit crab, as often happens in the case of 
recent shells, and from the appearance of the groove such an explana- 
tion seems well founded. The species is quite different from any of 
* the known west coast recent or fossil forms of this genus, being char- 
acterized by its exceedingly heavy shell, straight-sided conical spire, 
and obsolete revolving ridges. 
Named after Los Trancos Creek, near which the type was found. 
Type.—A decolleté specimen, L. S. J. U., No. 1082. 
Horizon.—Merced formation, upper Pliocene. 
Locality Santa Cruz quadrangle, Santa Clara County, locality 
No. 21, ditch between Feld Lake and Los Trancos Creek, 24 -miles 
south-southwest of Stanford University. (T. J. Hoover, R. Arnold.) 
Genus CHLOROSTOMA Swainson. 
CHLOROSTOMA STANTONI Dall, var. LAHONDAENSIS, new variety. 
Plate XXXVI, fig. 2 
Description—Shell attaining an altitude of 25 mm.; conoidal, 
much broader than high, umbilicated; whorls 5, angulate near base, 
upper surface sloping steeply, very gently concave both above and be- 
low a slightly raised line which revolves about two-fifths the distance 
from the suture to the angle; a second similar line revolves close to 
and just below the suture, and a much more prominent one adorns 
the angle of the whorl; body whorl biangular, the surface between 
