388 MARINE INVERTEBRATES 
M. lapilloides. The shell in this species is about an inch in length, 
and has markings which give it a striking resemblance to granite. A 
row of small round denticles upon the inner surface of the lip is a charac- 
teristic already noticed in some of the west-coast murices. Their station 
is the same as that of the purpuras— between the tides on rocky, 
exposed shores. (Plate LX XIII.) 
M. engonatum. This species has sharply ridged whorls, and re- 
volving ribs with wavy growth-lines between them. In other respects 
it is almost identical with the last described. It is often found mingled 
with the seaweed which covers rocks between tides, and, when moist, 
simulates the color of its surroundings. (Plate LX XIII.) 
Genus Chorus 
C. belcheri. This family cannot well be left without at least a 
mention of this large and rather handsome species. Chorus is a genus 
of but few species, confined to the Pacific shores of North and South 
America. This particular species does not reach as far north as San 
Francisco, but may be taken at low tide in the vicinity of San Diego. 
The prominent feature of the shell is the posterior canal, which, being 
abandoned as the growth of the shell continues, leaves a series of hol- 
low, folded spiny processes upon the shoulder of the body-whorl, which 
appear like jagged points upon the spire. (Plate LXXIII.) 
FAMILY COLUMBELLIDE 
This is a large family of small but often exceedingly beautiful 
shells. Their distribution is mostly tropical, but the list of 
North American species is a very generous one indeed if the 
deeper-water forms are included. The animal is quite the same 
as in the Buccinide, to be described later. (See also description 
of Buccinum undatum on page 330.) The shells are usually quite 
solid, with a long, narrow slit for an aperture; the outer lip is 
thickened on the inside, especially about the middle portion, and 
is deeply toothed; and the lower portion of the columellar lip 
is also ribbed or toothed. 
Genus Columbella 
C. mercatoria. This Antillean species is found in Florida, and is 
one of the gems among the American shallow-water shells. Its height 
is about one half of an inch. It is decorated with revolving grooves 
and with a variously patterned color-scheme of broken yellow or reddish 
. 
