46 LAND AND FRESH-WATER SHELLS. 



and the shell is said to be integripalliate ; those shells in which the 

 pallial line is not evenly described, but forms a sinus in relation 

 with the posterior adductor impression are said to be sinupalliate. 



Fig. 14. The anatomy o a iviussel, and the .Ktenioi markings of its shell, 



7. The lines of shifting of the muscles, numerous lines running 

 from the different impressions towards the umbo. 



8. The hinge, a longitudinal ridge running along the dorsal 



Fig. 13. Right valve of the shell of Cytherea showing internal markings. 



portion of each valve. The absence of teeth in the Anodon 

 shell ; in Unio, Splicer him, and Pisidium teeth obtain. The teeth 

 consist of three sets : cardinal teeth situated below the umbones, 



