9a. Posterodorsal corner of right valve produced into a long spine. Posteroventral margins of the carapace armed with row of strong teeth. Carapace covered with clear sculpture of oblique striae. Rostrum well-developed.
Step 10
9b. Posterodorsal corners of both valves rounded and spineless. Posterior margins of the valves lack teeth. Carapace either lacks sculpture, or has a very indistinct concentric pattern of striae. Rostrum small or normally developed.
Step 11