Tetrachaelasma southwardi Newman & Ross, 1971. Nomenclature used for the scuto-tergal articulation (the specimen shown in Fig. 4J–L is taken as a model). Scutum: A. Exterior view; B. Lateral view; C. Interior view. Tergum: D. Lateral view; E. Exterior view, smoothly concave articular margin painted in yellow; F. Internal view, sinusoidal articular margin painted in red. Abbreviations: a-a’ – distal and basal ends of the scutum articular ridge; b-b’ – distal and basal ends of the vertical articular ridge; c-c’ – distal and basal ends of the tergal articular furrow; laf – lower articular furrow; sar – scutum articular ridge; taf – tergal articular furrow; tar – tergal articular ridge; uaf – upper articular furrow; var – vertical articular ridge.