Description. Carapace subrectangular, its length and width approximately as 2 : 3; both the anterior and posterior angles approaching right angles in older specimens; anterior angles, however, more rounded than the posterior ones. Frontal margin varying in different specimens from slightly convex to gently emarginate; lateral margins moderately convex, posterior margin broadly concave. The greatest width is found in the middle between the anterior and posterior margins. The upper test carries but a very narrow thickened rim on the anterior and lateral margins; it is continued, however, into a very broad, concentrically furrowed doublure on the underside, which in front attains one sixth the length of the carapace and becomes reduced to one half that width toward the genal angles. The eyes are very large (one third of length of carapace); much elevated, furnished with a semicircular, narrow visual area; approximate, about their own length apart, situated a little forward of the bisecting line. The ocelli are situated on a prominent, heart-shaped mound between the posterior extremities of the lateral eyes. The surface is covered with closely arranged prominent tubercles which along the frontal margin are arranged in concentric rows.
The first tergite is short and wide and like the following furnished with a row of large tubercles along the posterior margin.
| Measurements of type [first specimen figured, 1907, pl. 6, fig. 1]. | millimeters | |
| Length of carapace | 12.3 | |
| Width | 16.5 | |
| Width of doublure | 1.5+ | |
| Length of lateral eye | 2.5 | |
| Distance between visual surfaces | 9. | |
| Exposed length of first tergite | 1.2 | |
| Width | 12.4 | |
| The smallest carapace observed measured | ||
| Length of carapace | 3.5 | |
| Width | 5.5 | |
| Length of lateral eye | .9 | |
| Distance between visual surfaces | 4. | |
