Tetracyclus Rupestris Guide
Credit: Ian Bishop
  1. Valves elliptic-lanceolate
  2. Septae distinct
  3. Costae robust, parallel
  4. Rimoportula present

Valves are elliptic-lanceolate, with broadly rounded apices. Septae are distinct and extend approximately 1/4 of the way into the valve. Septae alternate orientation from one band to the next. Costae are robust and parallel. A single rimoportula is present at one valve end.