200 AMERICAN MARINE CONCHOLOGY. 



the beak and extending about one-third the length of the shell ; 

 haemal valve with a mesial septum of about the same length 

 extending forward from the beak. 



1. G. PYRAMiDATA, Stimpson. Fig. 551. 



{Lingula ) Am. Journ. Sci., xxix. 444. 1860. 



Shell greenish-white, ovate, elongated, convex ; base subtruncate ; 

 surface smooth and glossy ; incremental lines inconspicuous. 



Length 22, width 9 mill. 



North Carolina. 



The mantle has well-developed marginal setse, those on either 

 side, at the extremity longer than the rest, equalling in length 

 one-third the width of the shell. There are two black spots on 

 the margin of the mantle at the extremit}-. Peduncle, thick, 

 muscular, hyaline with an opaque axis, three times the length of 

 the shell. 



This species has been found, so far, unattached. It is extremely 

 active in its motions when disturbed, and has the power, as 

 described by Mr. Morse, of burrowing in and travelling over the 

 sand by contortions of the peduncle and movements of the seta?. 

 Furthermore, the soft parts secrete a mucus to which grains of 

 sand adhere, forming a " sandtube" of an extremely ephemeral 

 nature, which sometimes extends over part of the valves. 



