ANATOMY OF TllK CLAM. 



6? 



siphon below the lenticular body ma — to the mouth, which is 

 ated al the auterior end of the shell, opposite the siphon '1 

 ing is simple, unarmed, without lips, and often diffi- 

 cult to detect. On each side of the mouth is a pair 

 of flat, narrow pointed appendages called palpi. The c 

 digestive canal passes through a dark rounded ma 

 mostly consisting of the 1 i \ <r. covered externally by 

 the ovarian masses. The mouth has no teeth, and i 

 oesophagus leads to a tubular stomach and intestine, 

 the latter loosely coiled several times and then passing fiq :i. Heart 

 Btraight backwards along the dorsal side under the ",l ""' clam. 

 lunge and directly through the ventricle ot the a, aui 

 ending posteriorly opposite the excurrent di- ['j'n s l,a> 

 vision of the siphon. Through the body pass< - a 

 curious Blender cartilaginous rod, whose use is unknown, unl< 

 be to support the voluminous viscera. Tin or branchia 



four large, broad, leaf-like folds of the mantle, two on a side, hang. 



75. - Circulatory system of • a fresh water mussel. I, ventricle; 



•»'. arterial system; 14 and r>. veins which follow the border of the nee 

 The veins lead the blood in pari directl} towards the organ -4, which if 

 kidnej pr "organ of Bojanus," and in pari to the venus sinus of the upper 



BUrfai t this organ; 5, veins which carry back the blood from the l-iIIs, t Ik- 



rest going to the sinus, 8, where arise the branchial artei 

 chial veins, and '.', the gill; 16, the foot. 



ing down and covering each side of the body (Fig. 72, D, a). The 



Fig. 74) is contained in a delii . called the 



and is situated immediately under the hinge; it consists of a 

 tricle and two auricles; the former is easilj n I by the 



passage through it of the intestine (Fit 7'.', 1>. v), usu 

 orcd dark, and by its pulsations. The two wing-like auri 

 broad, somewhat trapezoidal iu form. Just behind the ventricle is 



