MESODOX. 145 



Triodopsis loricata, Gld., Tri-o-dop'-sis lor-i-ca'-ta. 



The shell of this little creature is only a quarter of 

 an inch in diameter, but it is a perfect five and a half 

 whorled spiral, having an open umbilicus and a 

 slightly raised spire. The aperture is irregular, with 

 a white tooth on the columella and two white, thick- 

 ened spots on the outer lip; the surface of the shell 

 is light horn-colored. It is found near Oakland, Cal- 

 ifornia, and in other parts of the state. 



An Oregonian species, which we will now consider 

 and which may be easily recognized by its peculiar 

 features, is named Mesodon devius, Gould, Mes'-o-don 

 de'-vi-us. The shell is yellowish horn-colored, solid, 

 and six-whorled; the umbilicus is partly covered, and 

 the peristome is white, wide, and bent back at right 

 angles to the walls of the aperture. There is a dis- 

 tinct white tooth on the inner wall of the aperture, 

 and sometimes one or more waves on the peristome. 

 There are several varieties which range in diameter 

 from a half to a whole inch. 



Mesodon Cohimbianns, Lea, Co-lum-bi-a'- nus. 

 Fig. 130. 



The shell of this little snail greatly re- 

 sembles some varieties of the last species. 

 Its spire is more acute, and the epidermis 

 on the upper whorls is set with short, stiff, 

 microscopic hairs, making the shell feel 

 rough. Whorls six, umbilicus small, peristome wide, 

 reflected, whitish, aperture ear-shaped. In some 

 varieties, as shown in the cut, there is a small white 

 tooth on the inner wall of the aperture. The shell is 

 of a light horn-color, and its diameter is over half an 

 inch. It is found chiefly in Oregon and Washing- 

 ton, but it extends into California, and even into 

 Alaska. < 10 > 



