194 FEESH-WATEE. AQTJAEIA. 



margiu, and the posterior side or end tapers to a wedge-like 

 point. The lunule is narrow, and the ligament short and 

 prominent. There are four strong teeth attached to the 

 hinge — ^two cardinal and two lateral. The mnsoular scars 

 are quite distinct. M. Moquin Tandon is reported to have said 



Fig. 128. Unio tumidus. 



that this animal, in July and August, emits small elongated 

 pointed masses, each containing about 100 eggs, and a single 

 mollusc of this species has been known to lay about 150 of 

 such masses in a few days. 



Unio pictormn is a species found in the sluggish and 

 stagnant water of England, but not, it is said, farther north 

 than Yorkshire. The foot of the animal is reddish. The 

 orifices are very like those of U. tumidus. The shell is about 

 2iin. long and more than lin. high : it is not so thick as that of 

 the last species, and altogether has a slimmer appearance. The 

 colour is yellowish-brown, marked with darker brown bands. 

 The anterior side slopes away towards the ventral margin, 

 which is almost straight. The posterior side gradually tapers 

 each way, but principally from the dorsal margin, until it 

 comes to a round point. The umbones are towards the anterior 

 extremity, and turn a little in. Both the lunule and the 

 ligament are rather long : the former is narrow. There are 

 four teeth, but they are not so strong as those of Z7. twrnid/us. 

 The muscular scars are distinct, and the pallial scar is not. 

 One individual of this species has been said to lay the extra- 



