444 Mr. Children's Abstract of the Characters of 



body falls 16'044 feet per second; not 16 T \ feet, as according 

 to Thomas Simpson, — 



2dly, If the earth's equatorial radius be 20,927,442 feet ; 

 not 21,000,000,— 



3rdly, If a sidereal day contain 86,164 mean solar seconds; 

 not 86,160,— 



The gravity at the equator is to the centrifugal force as 

 1 to j^. 7J , and the ellipticity ^ y ; not ¥ | T , as according to 

 T. Simpson : the difference is not much. 



And as we know from observations with the pendulum that 

 the ellipticity is less, the polar section of the earth is not an 

 exact ellipse, and the usual reduction of the observed latitude 

 (tan A = (1 — e 9 ) tan I) not strictly correct. 

 Canonbury. SAMUEL SHARPE. 



LXXIV. An Abstract of the Characters of Ochsenheimer's 

 Genera of the Lepidoptera of Europe; with a List of the 

 Species of each Genus, and Reference to one or more of their 

 respective Icones. By J. G. Children, F.R.S. L. fy E. 

 F.L.S.Sfc. 



[Continued from page 354.] 



Genus 19. ZYG^ENA, Fab., Latr., Hiibn. 

 Anthrocera, Scop. (Steph.) 



Legs, tibiae with short, close-set scales; the posterior with 

 very small calcaria, or spines. (Latr.) 



Wings, deflexed, (Latr.) broad ; anterior generally steel-blue, 

 with red spots; posterior generally red. 



Antenna slender at the base, thickening into an abrupt, bent 

 fusiform club, with the apex simple ; in the males robust. 

 (Steph.) 



Palpi reaching beyond the clypeus, cylindric-conic, acumi- 

 nated, densely clothed with hair. (Steph.) 



Antlia fine, moderately long. 



Abdomen nearly cylindrical, obtuse; (Latr.) thickly clothed 

 (as well as the head and thorax) with short silken hairs, 

 with a few scales intermixed. (Steph.) 



Flight, diurnal. 



Larva, villose, fusiform, generally spotted with black on a 

 pale ground; head small. (Steph.) No horn on the last 

 segment of the body. (Latr.) 



Pupa elongate. (Steph.) 



Metamorphosis in the air, in a pretty solid silken cocoon, at- 

 tached to the branch or leaf of a plant. (Latr.) 

 Obs. These insects are sluggish, and fly but little ; they 



commonly 



