 In his 1935 work Handbuch der <unk> <unk> ( Handbook of Systematic <unk> ) , Johannes Thiele introduced a mollusc taxonomy based upon the 1909 work by Cossmann and <unk> . Thiele 's system divided the bivalves into three orders . <unk> consisted of forms that had <unk> dentition , with a series of small parallel teeth perpendicular to the hinge line . <unk> consisted of forms that had either a single adductor muscle or one adductor muscle much smaller than the other . <unk> consisted of forms with ctenidial gills . The <unk> was further divided into four suborders : <unk> , Heterodonta , <unk> and Anomalodesmata . 
