Rhomb plate
From dinoflaj3
The midventrally located plate immediately anterior to the anterior sulcal plate and commonly contacting the apical pore complex. In the Kofoid tabulation system it is the first apical plate (1') or its homologue (*1'); in the Taylor-Evitt tabulation system it is designated 1u; in the Edwards tabulation system it is designated as the R plate. Refer to Text-Figure 60.