Spencer), as in the Araneae and Opiliones, and, on the other hand, may terminate in simplification and degeneration, as in the Acari.
2nd) somite (Opiliones) of the opisthosoma, there being rarely an additional stigma on the 4th (some Solifugae).
Remarks on the Opiliones.
The Opiliones seem to lead on from the Spiders to the Mites.
Apparently related to the Opiliones are two extinct groups, the Anthracomarti and Phalangiotarbi, which are not known to have survived the Carboniferous period.
I Opiliones; after Thorell.
Hansen and Sorensen, On Two Orders of Arachnida (Cambridge, 1904); Sorensen, " Opiliones laniatores," Nat.
Orders: Pedipalpi, A raneae, Palpigradi, Solifugae, Pseudoscorpiones, Podogona, Opiliones, Rhynchostomi (Acari).
- Degenerate Arachnids resembling the Opiliones in many structural points, but chiefly distinguishable from them by the following features: - The basal segments of the appendages of the 2nd pair are united in the middle line behind the mouth, those of the 3rd, 4th, 5th and 6th pairs are widely separated and not provided with sterno-coxal (maxillary) lobes, and take no share in mastication; the respiratory stigmata, when present, belong to the prosoma, and the primitive segmentation of the opisthosoma has entirely or almost entirely disappeared.
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