MARINE MOLLUSCS 



213 



leaving its siphons exposed at the surface. It inhabits deep water, 

 and is not likely to be obtained without the use of the dredge or 

 trawl. 



The molluscs of the family Lucinidce are found principally in 

 tropical and sub-tropical seas, ranging from the shore to a very great 



Fio. 144. Cyprinidce 



1. Cyprian islandiea. 2. Teeth of Cyprina. 3. Astarte compresta. 4. dree minima. 

 5. Isoeardia tor 



depth, but a few are moderately common in our own waters. They 

 are closely allied to the Cyprinidce, but the shell is round rather 

 than oval, and is obliquely grooved inside. The mantle lobes of 

 the animal are not united on the ventral side, but at the posterior 

 end they are continuous, except where they form one or two siphonal 

 openings. The foot is long and of almost the same thickness 



