Achanthoceras Zachariasii Guide
  1. Frustules lightly silicified
  2. Valves with long extensions
  3. Girdle bands numerous
  4. Resting spores distinct

Frustules are lightly silicified and typically lie in girdle view. Valves have two long horn-like extensions. Girdle bands are numerous. Resting spores are distinct, and resistant to processing, while the delicate frustules are easily destroyed.