Barry S C Leadbeater, John van den Hoff
A detailed morphological and quantitative study of Stephanoeca norrisii Thomsen has revealed that the two-chambered lorica contains an outer layer of 25-30 longitudinal costae. Additional single longitudinal strips occupy the spaces between the longitudinal costae in the anterior chamber. Within the framework of longitudinal costae there are four bands of horizontal costae labelled A-D. Band A comprises an anterior ring. Bands B and C of the anterior chamber combine to form a multistranded partial left-handed helix containing 30-50 costae, each costa containing three strips. Band D extends from the lower part of the anterior chamber to the base of the posterior chamber and comprises a multistranded left-handed helix containing 12 costae that undergo one turn of 360°. In total the lorica contains between 400 and 500 costal strips. Whilst aspects of the lorica resemble another Stephanoeca species, the unique feature of additional single longitudinal strips and the organization of the inner costal bands are sufficiently different as to warrant this species being attributed as the generic type to Ellisoeca gen. nov. Two other forms with a graded series of similar lorica characters are also attributed to this genus as E. burtonii sp. nov., and E. canistra sp. nov.