The genera used in the tabulation were: Calymene, Dipleura, Goldius, Proëtus, Cyphaspis, Acidaspis, Phacops, Hausmania, Coronura, Odontochile, Pleuracanthus, Calmonia, Pennaia, Dalmanites, Probolium, and Cordania.
The trilobites of the late Palæozoic (Mississippian to Permian) belong, with two possible exceptions, to the Pröetidæ, and only three genera, Proëtus, Phillipsia, and Griffithides, appear to be known from all the parts. I am, however, assuming that both Brachymetopus and Anisopyge have 9 segments in the thorax, and so have tabulated five genera. The range in the number of segments in the pygidium is large, from 10 in some species of Proëtus to 30 in Anisopyge, and the average, 17.3, is high, as is the average for total number in the trunk, 26.3. Anisopyge, a late Permian trilobite described by Girty from Texas, is perhaps the last survivor of the group. It seems to have had 39 segments in the trunk, making it, next to the Cambrian Pædeumias and Menomonia, the most numerously segmented of all the trilobites.
The above data may be summarized in the following table:
| Period | No. of genera | Av. No. of segments in thorax | Av. No. of segments in pygidium | Av. No. of trunk segments |
| Lower Cambrian | 19 | 13.90 | 03.70 | 17.60 |
| Middle Cambrian | 33 | 10.50 | 05.90 | 16.40 |
| Entire Cambrian | 62 | ... | ... | 17-19 |
| Ordovician | 40 | 10.15 | 08.81 | 18.96 |
| Devonian | 16 | 11.00 | 11.20 | 22.20 |
| Late Palæozoic | 05 | 09.00 | 17.30 | 26.30 |
This table confirms that made up by Carpenter, and shows even more strikingly the progressive increase in the average number of segments in the trunk throughout the Palæozoic.
While the two trilobites with the greatest number of segments are Cambrian, yet on the average, the last of the trilobites had the more numerously segmented bodies. The multisegmented trilobites are:
| Period | Genus | Av. No. of segments in thorax | Av. No. of segments in pygidium | Av. No. of trunk segments |
| Lower Cambrian | Pædeumias | 44+.... | 01 | 45+ |
| Upper Cambrian | Menomonia | 42..... | 04 | 46. |
| Ectenonotus | 12..... | 22 | 34. | |
| Ordovician | Encrinurus | 11..... | 22 | 33. |
| Dionide | 06..... | 26 | 32. | |
| Silurian | Harpes | 29..... | 03 | 32. |
| Devonian | Coronura | 11..... | 23 | 34. |
| Dalmanites | 11..... | 23 | 34. | |
| Permian | Anisopyge | 07+(9?) | 30 | 39? |
Anisopyge, the last of the trilobites, stands third on the list of those having great numbers of segments, and in each period there are a few which have considerably more than the average number. It may be of some significance that of these nine genera only Pædeumias and Anisopyge belong to the Opisthoparia, the great central group, and that five are members of the Proparia, the latest and most specialized order.