MARINE UNIVALVES 159 



means a net, or more properly, a basket that is used 

 for taking fish. Most of the members of this genus 

 are small, and the sides of their shells have a reticu- 

 lated surface, somewhat like network or the sides ot 

 a basket. Much as we regret it, however, it now seems 

 as if this good old Lamarckian name would have to 

 give place to another in the near future. But for the 

 present we will not anticipate any such change. 



Our largest member of the genus is 

 named Nassa fossata^ Gld., the Chan- 

 neled Nassa, Figure 144. The spire is 

 conical and ends in a pointed apex. 

 The surface of the whole shell is 

 marked with spiral and transverse 

 ridges, the former of which appear 

 also within the outer lip. The thick- 

 ness of this lip varies much with the 

 age of the animal, as does the callus ^j^ ^^^ 



of enamel which is spread over the 

 columella. This enamel, in mature specimens, is of 

 a bright orange color, and contrasts finely with the 

 light ash-color of the general surface of the shell. 

 The canal is short and abruptly reflected, while just 

 above it is a deep ditch, or fossa, showing at once 

 from what fact the specific name is derived. The 

 use of the canal seems to be to afford space and 

 protection for a breathing-tube, which projects above 

 the surface of the mud which the animal is exploring 

 for his prey. 



The Nassas are active mollusks, and are cordially 

 hated by the oystermen, because they are so prone 

 to bore holes through the shells of young oysters, 



