MORSE: OBSERVATIONS ON LAMELLIBRANCHS. 
149 
The two palpi much folded with ends recurved project Bome 
distance beyond the posterior edge of the slicll and between these 
and the base of the syphons is seen the syphoual tentacle which 
reaches beyond the ends of the syphons. The syphons are closely 
united to the tips. A distinct line marks the so{)aration of the 
two tubes. The anal syphon is less in diameter than the branchial 
one. The openings of the tubes are on a line, so to speak, though 
at times the anal tube projects a little beyond the branchial tube. 
No trace of papillae was discovered on either opening, nor was a 
Fio. 5. — Yoldia sapolilla (Gould). 
trace of a valve detected. The anal tube at times collapses, 
then expands on contraction of the body and closing of the shell. 
The mantle tubercle near the anterior end is very prominent 
and well defined, resembling a wart-like excrescence with an oval 
flattened surface. When the shell closes the face of the tubercle 
turns slightly outward. The lines of growth on the epidermis 
are slightly deflected by the growth of the tubercle. The foot 
is sharp-pointed, with its edge digitated. On August 21, the 
eggs were discharged in clouds. 
YOLDIA LIMATULA (Say). 
Fig. 6. Length, .57 mm. 
The characters of the expanded parts of this species are similar 
to those in Yoldia sapotilla with good specific differences. The 
posterior expansion of the mantle embracing the base of the 
syphons is larger than that of 1'. sapotilla and the margin is 
less folded as shown in the figure. The rounded lappet below is 
much smaller and the papillae fringing it are larger and few in 
number. The syphonal openings vary: the anal one somewhat 
