138 MOLLUSCA 



3. Open the shell by breaking the edge, inserting a knife 

 blade through the opening, and cutting the adductor muscle 

 away from the flattened right valve of the shell and notice 

 the single adductor, extensive gills, and the absence of a foot. 

 The larval oyster has a foot, but this is lost early in life. 



Brooks: The Oyster. 



Grave: Maryland Shell-Fish Commission, 4, Rep., 1912. 



Horst: On the Development of the European Oyster (Ostrea edulis, 



L.). Quart. Jour. Mic. Sci., 22, 1882. 

 Nelson: The Attachment of Oyster Larvae. Biol. Bull., 46, 1924. 



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 My a. 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 chamber correspond to typical siphons? See if 

 you can find how the animal swims. Is the movement con- 

 tinuous or jerky? Does the animal move forward or back- 

 ward? 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 

 .together and see how rounded the margins appear. Examine 

 a shell from which the animal has been removed by macera- 

 tion and see the relation of the shell cuticle and the cal- 

 careous 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 ARENARIA (Long Clam) 



This animal belongs to the order Eulamellibranchia, as 

 does Venus, and is introduced because of adaptation for its 

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



