332 PATELLID. 
SCUTELLINA, Gray. Shell with a broad margin internally. 7 
sp. Red Sea, Philippines, Pacific, Panama. A. crenulata, Brod. 
PrctinoponTA, Dall. 
Distr.—P. arcuata, Dall. West Indies. 
Shell resembling Acmeea, with a blunt subcentral apex. 
Animal blind, with the front part of the head between the 
tentacles and above the muzzle much produced upward and 
forward, extending considerably further forward than the end of 
the muzzle. Muzzle marginated, with lappets at the outer 
corners. Jaw thin, translucent. Gill exactly as in Acmea; 
sides of foot and mantle-edge simple, nearly smooth. 
Lortia, Gray. 
Syn.—Tecturella and Tecturina, Carp. 
Distr.— L. gigantea, Sowb. (1xxxiii, 22). West Coast of N. 
America. 
Shell patelliform, depressed, the apex anterior. 
Animal with a single cervical branchia, but also furnished 
with a branchial cordon of lamin between the mantle-edge and 
the foot, extending as far forward as the adductor muscle on 
each side and continuous behind; frill of the muzzle without 
lappets. The typical and only species is among the largest and 
most active of limpets, the shell attaining three inches in length. 
Scurria, Gray. 
Distr.—Several sp. West Coast of North and South America. 
S. scurra, Lesson (1xxxiv, 48). 
Shell patelliform, conical, elevated, rather thick and of rude 
growth. Branchiz completely surrounding the body, as in 
Patella, but having also the cervical plume of Acmea; muzzle 
without lappets. 
SCURRIOPSIS, Gemmellaro. Shell with radiating riblets crossed 
by concentric growth-lines. Jurassic. 
SuspraMiny PATHLLINA. 
Shell conical, with the apex turned forward ; muscular impres- 
sion horseshoe-shaped, open in front, as in the preceding groups. 
Animal. Gills forming a row of leaflets surrounding the body ; 
no cervical plume-like gill; radula provided with three lateral 
teeth on each side, and three uncini; rachidian tooth rarely 
present (xii, 51). : 
The continuous series of branchial lamelle forming a fixed 
cordon between the mantle and foot, together with peculiarities 
of their lingual dentition, serve to distinguish this subfamily 
from the preceding one. These animals are strictly littoral in 
habit, living upon the rocks between tide-marks; they are 
chiefly sedentary, adhering firmly by atmospheric pressure, and 
