262 SIX NEW SPECIES 



a few minutes after it was changed, they as uniformly com- 

 menced the passage of this constant stream. I cannot sup- 

 pose this operation to he for the sole purpose of breathing, as 

 there is no intermission in the stream of the water, and the 

 quantity thrown out. is too great for this purpose only. I 

 believe it to be the result of the action of the separation of the 

 animalcula from the water. 



Lamarck informs us that the animal of the anadonta (which 

 is essentially the same with the unio) is hermaphrodite and 

 seems viviparous ; for the eggs pass into the oviduct placed 

 along the superior branchiae, where the young are found with 

 their shells complete. In the dissection of an anadonta undu- 

 lata nearly three inches long, I met with the oviducts 

 charged with about 600,000 (as nearly as I could calculate) 

 young shells perfectly formed, both valves being distinctly 

 visible with the microscope. 



There cannot be a doubt that the two pairs of muscles, 

 which support the foot and serve by their alternate action to 

 give the animal locomotion, are entirely distinct from the 

 great anterior and posterior muscles, which seem but to serve 

 the purpose of closing the valves opened by the elasticity of 

 the ligament. The cicatrices of the muscles of the foot, ante- 

 riorly, are placed under the great anterior cicatrix, posteriorly 

 over the great posterior cicatrix, and are sometimes confluent 

 with the great cicatrices, sometimes entirely distinct from 

 them. 



It is necessary to notice here another set of attaching mus- 

 cles, which seem to have escaped attention. We find, on 

 closely examining the region of the cardinal tooth, a small ir- 

 regular row of muscular impressions. In those species which 

 possess large lobed teeth, these will be found generally on the 

 inner side of them and somewhat underneath. In the more 

 fragile shells, possessing comparatively small teeth, such as 

 the alatus, gracilis, &c. we find these impressions in the 

 cavity of the valve beneath the beaks. To this part of the 

 shell I found in many species the animal to be quite strongly 

 attached. It seems to serve to support the mantle, branchiae. 



