178 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
For years this shell was regarded as the young of Venus mer- 
cenaria. Professor George H. Perkins (Proc. Boston Soc. Nat. 
Hist., 1869, vol. 13, p. 148) discovered that the creature was 
ovo viviparous. In one shell he found thirty-six young ones. 
He says, "These young shells were oval, flat, transparent, 
longer than broad, the reverse of what is usual in the adult." 
The date of this gravid condition was in January, in New Haven. 
In an examination of a number of specimens of Gemma collected 
on Annisquam Beach, Cape Ann, in the month of July, I found 
the young shells, as described by Professor Perkins, near the 
Fig. 32. — Gemma gemma (Totten). 
beak anteriorly. The animal has a large foot and crawls freely, 
twirling the shell back and forth as it progresses. The syphons 
are united and are half aS long as the length of the shell. The 
branchial tube is slightly larger and somewhat longer than the 
anal tube. The branchial opening is fringed with nine or ten 
simple papillae. The valve is very long, narrow, and tubular. 
The syphons slowly protrude without the valve showing; sud- 
denly with explosive force the valve pops out like a flash. This 
behavior is unique. No trace of papillae was observed on the 
anal syphon. The creature is very sluggish and timid. 
I 
