122 LAMBERT: CONSTITUTION OF THE EARTH 



A', habeli Stearns, and variety ierebra Reibisch. 

 A'". indefaiigabiUs Dall. 



This group appears to be restricted to the arid zone of Chatham 

 Island, except the last species which is reported from Indefatigable 

 and James Islands. The species are very slender, with very numerous 

 whorls usually axially ribbed, with a solid slender and twisted axis 

 and unarmed aperture. 



Group of N. canalifcrus {Pelecostoma Reibisch). 

 N. canaliferiis Reibisch. 



This peculiar species has been found by Wolf only on Chatham 

 Island on moss and ferns at from 900 to 2000 feet elevation. It has 

 numerous flat-sided short whorls, a basal attenuation with a relatively 

 large funicular umbilicus, and a prominent flange on the pillar, which on 

 sectioning the shell is seen to continue as a strong concave plate, sur- 

 rounding the axis and continued into the penultimate whorl, gradually 

 becoming less prominent. Specimens were obtained by Ochsner from 

 the dry zone, near the beach to 450 feet elevation. Reibisch's second 

 species of Pelecostoma is TornaielUna chathamensis . 



GEOPHYSICS. — The internal constitution of the earth. Wai^ter 

 D. Lambert, U. S. Coast and Geodetic Survey.^ 



The title of this paper, "The internal constitution of the earth," 

 was chosen chiefly for brevity. Many of the topics included 

 under that comprehensive heading I shall not touch on at all, 

 and shall deal chiefly with the mechanical properties of the matter 

 in the interior of the earth, and more particularly with its density 

 and its elasticity. 



The view that generally prevailed down to recent times and 

 that still persists to some extent as the dictum of popular science 

 is that the interior of the earth is fluid and fiery hot, like molten 

 lava. The volcanoes seem to be offering us samples of the matter 

 within; mediaeval theologians saw in the hot interior of the 

 earth the future abode of sinners. The molten mass of the 

 earth is assumed to have cooled to some extent, thus forming on 

 the outside a crust of undetermined thickness, upon which we 

 live. 



^ The substance of this paper was read before the Maryland-Virginia- District 

 of Columbia Section of the Mathematical Association of America on December 6, 

 1919. 



