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"Acorn-shell (Balanus tintinnabulum). T., tergum; CR., thoracic legs; R., outer shell in section; D., aperture of oviduct; F., mantle cavity; X., depressor muscle of tergum; AN., antennae; OV., ovary; G., depressor of scutum; H., oviduct; AM., adductor muscle of scuta; S., scutum." -Thomson, 1916

Acorn Shell

"Acorn-shell (Balanus tintinnabulum). T., tergum; CR., thoracic legs; R., outer shell in section; D.,…

"Diagram of the dorsal surface of Limulus polyphemus. oc, Lateral compound eyes. oc', Central monomeniscous eyes. PA, Post-anal spine. I to VI, The six appendage-bearing somites of the prosoma. VII, Usually considered to be the tergum of the genital somite, but suggested by Pocock to be that of the otherwise suppressed praegenital somite. VIII to XIII, The six somites of the mesosoma, each with a movable pleural spine and a pair of dorsal entopophysis or muscle-attaching ingrowths. XIV to XVIII, The confluent or unexpressed six somites of the metasoma." — The Encyclopedia Britannica, 1910

Limulus Polyphemus

"Diagram of the dorsal surface of Limulus polyphemus. oc, Lateral compound eyes. oc', Central monomeniscous…

"Ventral view of the posterior carapace or meso-metasomatic (opisthosomatic) fusion of Limulus polyphemus. The soft integument and limbs of the mesosoma have been removed as well as all the viscera and muscles, so that the inner surface of the terga of these somites with their entopophyses are seen. The unsegmented dense chitinous sternal plate of the metasoma (XIII to XVIII) is not removed." — The Encyclopedia Britannica, 1910

Limulus Polyphemus

"Ventral view of the posterior carapace or meso-metasomatic (opisthosomatic) fusion of Limulus polyphemus.…

"Schizomus crassicaudatus, a Tartarid Pedipalp. Dorsal view of a male with the appendages cut short. I to VI. The prosomatic appendages. a, Anterior plate. b, Posterior plate of the prosomatic carapace. prae-gen, Tergum of the praegenital somite. II, The eleventh somite of the opisthosoma. pa, Post-anal lobe of the male—a conical body with narrow basal stalk." — The Encyclopedia Britannica, 1910

Schizomus

"Schizomus crassicaudatus, a Tartarid Pedipalp. Dorsal view of a male with the appendages cut short.…

"Restoration of Triarthrus Becki, Green, as determined by Beecher from specimens obtained from the Utica Slates (Ordovician), New York. A, dorsal; B, ventral surface. In the latter the single pair of antennae springing up from each side of the camerostome or hypostome or upper lip-lobe are seen. Four pairs of appendages besides these are seen to belong to the cephalic tergum. All the appendages are pediform and bi-ramose; all have a prominent gnathobase, and in all the exopodite carries a comb-like series of secondary processes." — The Encyclopedia Britannica, 1910

Triarthrus

"Restoration of Triarthrus Becki, Green, as determined by Beecher from specimens obtained from the Utica…