having completed his work, and being no longer connected with the Survey, the specimens have been placed in the hands of the writer for study and illustration.
The specimens of shale containing these remains amount to more than twenty in number, some of them containing only fragments of the fossil crustaceans, and nearly all of them containing coal plants. Two of the fossils are very large and fine specimens, being nearly complete. Several other smaller specimens are essentially complete in their parts and well-preserved, though from extreme compression in the black shale it is difficult to see the details of the organs and the surface sculpture. Several of the fragmentary portions and separated organs of the fossils are very interestesting and instructive.
A critical examination shows what are apparently two very distinct forms, which can be clearly characterized, besides other portions of much larger forms, which are at present unknown in their entire condition. All the better preserved specimens, as well as all the separated members or fragmentary portions having any important significance, have been drawn in a very complete and artistic manner by Mr. George B. Simpson, and are reproduced in heliotype.
Although several species of this family have been described from the carboniferous rocks of Europe, we have heretofore known but a single species from rocks of the same age in America. In the American Journal of Science, Vol. 46, p. 21, 1868, Messrs. Meek and Worthen published the description of Eurypterus (Anthraconectes) Mazonensis from the coal measures of Grundy county, Illinois, and the same is illustrated and farther described in the third volume of the reports of the Geological Survey of Illinois, page 544, 1868. The accompanying illustration, with the explanations, is copied from the volume cited:
