364 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Haven, Nantucket and Wood's Holl, and it extends as far 

 south as the shores of Florida. 



From the above remarks it will be noted that Anurida 

 maritime/, is a form ranging into both the Palsearctic and 

 Nearctic regions. This wide distribution of an animal 

 with practically no means of self-dispersal is remarkable. 

 Folsom (63) believes that marine currents have been the 

 principal agents for its distribution. They would 

 certainly account for its presence on the barren rocky 

 islands off the Scandinavian coast and at Heligoland and 

 the Isle of Man. 



An allied terrestrial species, Anurida (Aphoromma) 

 granaria (Nic), has likewise a very wide geographical 

 distribution. It has a very extensive range in Europe, 

 being known from Great Britain, France, Scandinavia, 

 the Tyrol and Bohemia, and it is also recorded in Arctic 

 regions from Spitzbergen, Franz-Josef Land and North 

 Siberia. ^4. tullbergi, Schott, which frequents the surface 

 of ponds of fresh water, is found in northern Europe and 

 has also been recorded from the United States. Another 

 species, A. davata, Schaff., is found in Tierra-del-Fuego ; 

 A. amorita, Fols., is known from Alaska and Siberia, and 

 A. steineni, Schaff, is a South Georgian species. 



IV.— MORPHOLOGY. 



1. General Features of External Anatomy. 



The general appearance of Anurida when viewed 

 under the lower power of the microscope will be seen on 

 referring to fig. 1. As in all insects, the body consists of 

 three well defined regions, viz., the head, the thorax and 

 the abdomen. Its exo-skeleton is but feebly chitinised, 



