MORSE: OBSERVATIONS ON LAMELLIBRANCHS. 
175 
Syphons short, broad at their bases, light yellow in color, 
mottled with light brown spots. Anal syphon represented by 
the valve which is long and tapering to a small opening and 
reaching some way beyond the opening of the branchiui tube. 
It is transparent, mottled with white spots. The branchial 
s\'phon is nearly twice the width of the anal tube, edge of its 
opening surmounted by long and short papillae alternating. 
The walls of the syphons show papillae sparsely distributed. 
At the ends of the syphons these are very small, increasing in 
size near the shell; they have pointed ends and are all recurved. 
Near the dorsal line they are more numerous. They spring up 
almost to the ligament of the shell. The anal valve is very 
mobile and stretches out till its opening is reduced to a minute 
perforation. The larger papillae are more like tentacles, indi- 
vidually moving and curving in various directions. 
CYTHEREA CONVEXA Say. 
Fig. 30. Length, 52 mm. 
A most sensitive creature. The closing of a door in a distant 
part of the house will cause the shell to shut instantly. The 
fringed mantle projects beyond the margin of the shell before 
Fio. 30. — Cytherea contexa Say. 
the syphons appear at all. The syphons are united and usually 
expand as long as half the length of the shell, or at times much 
longer. A deep groove marks their separation. A transverse 
