| Polar spines three-sided prismatic, cuspidate, about as long as the axis of the shell. |
| The premolars are characteristically very slender, sharp, and cuspidate. |
| Leaves much smaller, less oblique at the base, finely and regularly crenate, acuminate rather than cuspidate. |
| The serrations tend to be more nearly crenulate than cuspidate. |
| A gland cell is often associated with a sensory spot, a cuspidate spine, a seta, or an adhesive spine in segment 4 of male Pycnophyes and Kinorhynchus. |
