Note: This historical image is not a factually accurate paleontological restoration.
Reason: Multisegmented peduncle of chelicerae (unsegmented according to Selden 1984); subequal size of appendage II-V (appendage II short in Erettopterus).
You may ask further questions about the accuracy of this image at the image review page of Wikiproject Palaeontology on the English Wikipedia. Note that this image may be appropriate to illustrate obsolete paleontological views.
English: From Zittel’s Palaeontology. Pterygotus osiliensis, Schmidt. Silurian of Rootzikil. Restoration of the ventral surface, about a third natural size, after Schmidt.
a, Camerostome or epistoma. m, Chilarium or metasternite of the prosoma (so-called metastoma). oc, The compound eyes.
1 to 8, Segments of the sixth prosomatic appendage.
I′ to V′, First five opisthosomatic somites.
7′, Sixth opisthosomatic somite.
[Observe the powerful gnathobases of the sixth pair of prosomatic limbs and the median plates behind m. The dotted line on somite I indicates the position of the genital operculum which was probably provided with branchial lamellae.]
This image comes from the 13th edition of the Encyclopædia Britannica or earlier. The copyrights for that book have expired in the United States because the book was first published in the US with the publication occurring before January 1, 1929. As such, this image is in the public domain in the United States.