•204 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



It will be noticed from Table I. that no species 

 occur further north than 60 deg. N., and none further 

 south, than 50 deg. S. The most northerly point reached 

 is the coast of Norway where Sundevall found B. 

 lanceolatum, while A. hectori reaches furthest south, being 

 found off New Zealand. 



The majority of the species are found within the 

 belt of water between 40 deg. X. and 40 deg. S. of 

 the equator, so that the group is essentially tropical and 

 sub-tropical, with an occasional temperate extension 

 (see Table I.), and it is much more abundant in the 

 Northern than in the Southern Hemisphere. The genus 

 Bra nchio stoma is much more abundant than Asymmetron, 

 and is almost exclusively found in the Northern Hemi- 

 sphere while Asymmetron is about equally distributed in 

 both Hemispheres. Asymmetron is much more tropical 

 than Br anchio stoma, for while the former is only found in 

 one place outside tropical seas (A. hectori), the latter is 

 decidedly temperate and one species, B. lanceolatum, 

 approaches the Arctic circle. 



Table II. shows the distribution of the species in the 

 great seas of the world. It is noticeable that there 

 is scarcely a large tract of shallow water in the 

 whole world that does not possess at least one 

 species of the group, and we are led to believe that 

 far from having a discontinuous distribution as was 

 formerly supposed, it has a very continuous and wide- 

 spread distribution, as the latest expeditions show. 

 While the Atlantic Ocean possesses but three species of 

 the group, the Pacific Ocean, including the Indian Ocean 

 and the seas of Melanesia, have no fewer than fifteen 

 species, the Indian Ocean alone being the home of eight 

 species. Asymmetron is confined, with the exception of 

 one species (A. lucayanum found in the Caribean Sea, but 



