In the other venomous snakes (viperines and crotalines) the maxillary bone is very short, and is armed with a single very long curved fang with a canal and aperture at each end.
The teeth form a complete series in the under jaw, and in the upper jaw on the premaxillary and maxillary bones.
The so-called colubrine venomous snakes, which retain in a great measure an external resemblance to the innocuous snakes, have the maxillary bone not at all, or but little, shortened, armed in front with a fixed, erect fang, which is provided with a deep groove or canal for the conveyance of the poison, the fluid being secreted by a special poison-gland.
In the Decapoda, where the antennal gland alone is well-developed in the adult, the maxillary gland sometimes precedes it in the larva.
Thus, in the Phyllopoda, the antennal gland develops early and is functional during a great part of the larval life, but it ultimately atrophies, and in the adult (as in most Entomostraca) the maxillary gland is the functional excretory organ.
T, temporal muscle; m, masseter; m', portion of masseter transmitted through the infra-orbital foramen, the superior maxillary nerve passing outwards between it and the maxilla.
Appendages of 2nd pair not underlying the mouth, but freely movable and, except in primitive forms, furnished with a maxillary lobe; the rest of the limb like the legs, tipped with a single claw and quite unmodified (except in a').
There is a distinct alisphenoid canal for the passage of the internal maxillary artery.
In the true poisonous snakes the maxillary dentition has undergone a special modification.
The appendages of the two maxillary segments arise as treble instead of single projections, thus differing from other appendages.