170 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
ing suddenly to the normal sculpture; the latter begins with four rounded, 
somewhat undulated, strong, spiral cords with narrower interspaces; on 
the next whorl the cords have flattened out and the much narrower inter¬ 
spaces are channeled; on the subsequent whorls the cords become still 
flatter and wider and the interspaces narrow grooves, occasionally punctate 
from the intersection of the incremental lines, otherwise hardly visible; on 
the last whorl the grooves are obsolete on the middle of the whorl, but 
there are half a dozen feeble threads on the base and canal; the suture is 
closely appressed; aperture narrow, simple, outer lip hardly thickened, 
body erased, pillar with two prominent and one obscure plait; canal not 
differentiated. Height of shell, 14; of last whorl, 11; of aperture, 8 mm. 
(Dali.) 
Type in United States National Museum, No. 252998. Type locality, 
San Diego, California. 
Range. Catalina Island to San Diego, California. 
Mitra lowei Dali, 1903 
Plate 16, fig. 4 
Proceedings of the Biological Society of Washington, 16:173. Bulletin 112 , United 
States National Museum; PI. 15, fig. 4. 
Shell of a warm yellow-brown with a whitish apex; nucleus subtrochi- 
form, smooth, solid, of about three conical whorls; subsequent whorls (in 
the type specimen) about four, rapidly increasing in diameter; those which 
immediately succeed the nucleus marginated in front of the suture by two 
or three fine spiral grooves, the interspaces of which stand up like threads, 
but these gradually become less pronounced and hardly noticeable on the 
fourth whorl where the sculpture becomes on the periphery fine, very 
inconspicuous, and widely separated grooves, only noticeable under a lens, 
but minutely punctate; they become somewhat stronger on the base and 
canal; aperture wide and semi-lunate; pillar with three nearly horizontal 
plaits; the canal very short and wide. Length of shell, 5.5; of last whorl, 
4.5 ; diameter, 2.5 mm. (Dali.) 
Type in United States National Museum, No. 109305. Type locality, 
off Catalina Island, California. 
Range. Off Avalon, Catalina Island, California. 
Mitra idae Melvill, 1893 
Conchologist, 2:140; PI. 1, fig. 6. 
M. testa elongato-cylindrica, ponderosa, nigra epidermide omnino con- 
tecta, spira obtusa fusiformi, anfractibus septem, transversim, regulariter 
[170 1 
