oC - 



external sculpture of regular, closely-set concentric rugae, equ- 

 ally develoioed throughout and extending §^3?0ss the rostral carina 

 and escutcheon, but ceasing at the edge of the narrow lunule; teeth 

 strong, with about twenty before and fifteen behind the small ch^n- 

 drophore. 



Pi ensions .- length 8.8 mm.; alt. 5.8 nira. ; semidiam. 2.4 ram. 



Reinarlrs . - The typical forms of this soecies- the most pro- 

 lific of the Ledas- are characterized by their unusual, almost 

 rotund, shape, v/hich, together with the features of the limule and 

 escutcheon, permits such forms to be readily recognized. It is 

 not surprising to fine raarkec! variability in a f?roup which is so 

 well represented. The most r-arked variation is toward a more 

 elongate form and the end products are notably different from 

 the average form. A different appearance is presented by cer- 

 tain forms which are high, but have the posterior carin sharper 

 than usual, the escutcheon broader and the posterior and anter- 

 ior sulci more definitely developed. The presence of an area in 

 front of the beaks wrich differs in sculpture from the remainder 

 of the shell is employed as the criterior In assigning these two 

 antipodal tyoes to this species. The sculpture is, however, fair- 

 ly constant, although on a few forms the rugae are coarser than 

 on typical individuals. The posterior sulcus is seldom conspiciious , 



in fact, very few individuals display it to such a degree as the 

 one figured by Dall, and an anterior sulcus is but rsrely developed. 



