124 MOLLUSCA. 



SOLEMYA. 



This form, a member of the order Protobranchia, with much 

 the same structure as Yoldia, shows an interesting method of 

 swimming that should be compared with Pecten, and with the 

 jets of water formed by Mya. Specimens may be dug at low 

 tide from mud or sandy mud, placed in a dish of sea-water, 

 and observed. Does the posterior opening in the mantle cham- 

 ber correspond to typical siphons? See if you can find how the 

 animal swims. Is the movement continuous or jerky? Does the 

 animal move forward or backward? Is the foot active? Are 

 jets of water thrown from the shell? Is the animal adapted to 

 forming jets of water? 



Examine a specimen that has the valves closely drawn to- 

 gether and see how rounded the margins appear. Examine a 

 shell from which the animal has been removed by maceration and 

 see the relation of the shell cuticle and the calcareous portion of 

 the shell. What becomes of the marginal cuticle when the shell 

 is closed? Can this have anything to do with throwing jets of 

 water from the shell ? 



Drew: Locomotion in Solenomya and its Relatives. Anat. Anz., 17, 1900. 

 Stempell: Zur Anatomie von Solemya togata. Zool. Jahrb., 13, 1899. 



MYA ARENAK1A. (Long Clam.) 



This animal belongs to the order Eulamellibranchia, as does 

 Venus, and is introduced because of adaptations for its manner 

 of living. It lives buried in the mud, in which as an adult it 

 remains stationary. You should find a "clam bed" along the 

 shore, and after noticing the pits in 4 the surface of the mud, and 

 the jets of water that are sometimes thrown from the pits, dig 

 down and see how the animals are placed. If the water is calm, 

 see if you cannot find the openings of the siphons at the surface 

 of the mud, of specimens that are still covered by water. You 

 will need to walk very carefully so as to disturb mud and water 

 as little as possible, as the siphons are otherwise closed and 

 withdrawn. 



