No Crustacean exhibits this trilobite form.
- Five stages in the development of the trilobite Sao hirsuta.
40) is also similar to a Trilobite so far as its segmentation and trilobation are concerned.
Between the two and at the highest point of the arc, so far as morphological differentiation is concerned, stands the scorpion; near to it in the trilobite's direction (that is, on the ascending side) are Limulus and the Eurypterines - with a long gap, due to obliteration of the record, separating them from the trilobite.
The bi-ramose structure of the post-oral limbs, demonstrated by Beecher in the trilobite Triarthrus, is no more inconsistent with its claim to be a primitive Arachnid than is the foliaceous modification of the limbs in Phyllopods inconsistent with their relationship to the Arthrostracous Crustaceans such as Gammarus and Oniscus.
- Four stages in A B C D ° ```' the development of the trilobite Agnostus nudus.
- So-called " trilobite stage " of Limulus polyphemus.