THE NATURAL HISTORY SURVEY. 207 
short, cylindrical; foot grayish white in color, truncate before, 
bluntly rounded and flattened behind; a lateral groove runs 
from the head to the posterior part, just at the edge of the foot, 
and meets in anacute angle behind; respiratory orifice on right 
side, just beneath the peristome of the shell and near its junc- 
tion with the body-whorl; mantle colored like shell. Length 
of foot 26.00 mill., width 6.00 mill. 
- The heart is situated 3 mill. from the junction of the per- 
istome with the body wall, and the pulsations are very regu- 
lar. Fifteen experiments gave the following number of pulsa- 
tions per minute: 84, 82 (twelve specimens), 61, 50. The last 
two figures were taken when the animal was contracted, and 
the heart-beats much slower. 
Jaw: Arched, broad, ends broadly rounded; concave mar- 
Fic. 48. 
Radula of PyYRAMIDULA ALTERNATA Say. (From nature, after Pils- 
bry, Guide to Helices, pl. xi, figs. 18,25.) C, central tooth; 1, first lateral; 
11, first marginal; 27, sixteenth marginal; J, jaw. 
gin not very much crenulated, with a rounded median projec- 
tion; anterior surface marked by vertical striz (Fig. 48, J). 
Radula formula: 24+149+}4+19+2+ (34-1 — 34); central 
tooth with a subquadrate base of attachment, somewhat ex- 
panded on the lower outer corners; reflected portion with one 
long central cusp reaching below the lower edge of the base 
of attachment, and two very small side cusps with small cut- 
ting points; lateral teeth (ten perfect) longer than wide, bicus- 
pid, the inner cusp long and narrow witha long, narrow cutting 
point, and the outer cusp.short and wide with a short cutting 
point; marginals variable, at first like the laterals, but becoming 
wider toward the margin (twenty-seven) and with one long inner 
cusp and ashort outer cusp. The cutting point is generally 
one-third the length of the cusp (Fig. 48). There are about 120 
rows of teeth. 
