Maxillary vertically erectile, perpendicularly to ectoptery goid, and reaching quadrate or mandible: Viperidae.
- Without an external pit between eye and nose, and the maxillary bone is not hollowed out above.
The maxillary palps have usually three, the labial either two or four segments.
The palps, both maxillary and labial, have two segments.
Maxillary and labial palpi are also present, and the latter, together with the labrum or lower lip, form the rostrum.
The premaxilla is always unpaired, but each half has three long processes directed backwards; one fuses with the maxillary bone, another helps to form the anterior part of the palate, while the third, together with its fellow, forms the " culmen " and extends backwards to the frontals, or rather to the ethmoid which there crops up on the surface.
The nasal cavity communicates with the mouth by the choanae or posterior flares, situated between the palatine process of the maxillary, the palatine and the vomer.
1, Bd) are very intimately fused together to form what is called the "lower lip" or labium, a firm transverse plate representing the fused basal portions of the maxillae, which may carry a small median "ligula," representing apparently the fused inner maxillary lobes, a pair of paraglossae (outer maxillary lobes), and a pair of palps.
The bestknown family is the Hydrophilidae, in which the feelers are short with less than eleven segments and the maxillary palpi very long.
The appendages of the two maxillary segments arise as treble instead of single projections, thus differing from other appendages.
Appendages of 1st pair.tri-segmented, chelate; of 2nd pair chelate, with their basal segments subserving mastication; of 3rd, 4th, 5th and 6th pairs similar in form and function, except that in recent and Carboniferous forms the basal segments of the 3rd and 4th are provided with sterno-coxal (maxillary) lobes, those of the 4th pair meeting in the middle line and underlying the mouth.
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').
The segmentation of the prosoma and the form of the appendages bear a homoplastic similarity to the head, pro-, meso-, and meta-thorax of a Hexapod with mandibles, maxillary palps and three pairs of walking legs; while the opistho io i e d c b o a S' S" 2 I VT V S IV III II I Opisthosoma Prosoma FIG.
Appendages of 1st pair large, three segmented and completely chelate; of 2nd pair either simple and pediform, or prehensile and subchelate; of remaining four pairs, similar in form, ambulatory in function; the basal segment of the 2nd, 3rd and sometimes of the 4th pairs of appendages furnished with sterno-coxal (maxillary) lobe.
,?, VI B, Ventral view of the prosoma and of the first somite of the opisthosoma, with the appendages I to VI cut off at the base; a, tracheal stigma; mx, maxillary processes of the coxae of the 3rd pair of appendages; g,genital aperture.
In the true poisonous snakes the maxillary dentition has undergone a special modification.
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 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.
Maxillary vertical, loosely attached, toothed; mandible toothless; a single pair of pelvis bones: Typhlopidae.
Maxillary bordering the mouth, forming sutures with the premaxillary, prefrontal and frontal, toothless; lower jaw toothed; pubis and ischium present, the latter forming a symphysis: Glauconiidae.
Maxillary horizontal; pterygoid reaching quadrate or mandible.
Maxillary horizontal; pterygoid not reaching quadrate or mandible: Amblycephalidae.
- Burrowing snakes, mostly small, which have the body covered with smooth, shiny, uniform cycloid scales The teeth are restricted to the small maxillary bones.
The anterior maxillary teeth are grooved or "perforated."
The maxillary and dentary bones carry teeth on their whole length.
- One, or a few, of the posterior maxillary teeth have a groove or furrow in front, which conducts the secretion of the enlarged upper labial glands.
- The anterior maxillary teeth are deeply grooved, or so folded as to appear hollow or perforated.
The Gymnomera, with a carapace too small to cover the feet, which are all prehensile, are divided also into two tribes, the Onychopoda, in which the four pairs of feet have a toothed maxillary process at the base, and the Haplopoda, in which there are six pairs of feet, without such a process.
In all Trichoptera the maxillary palps of the female are fivesegmented.
In the Limnephilidae the maxillary palp is three-segmented in the male, the larvae are variable in habit, many forming cases of snail-shells.
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.
There is a distinct alisphenoid canal for the passage of the internal maxillary artery.
The mandibular somite bears a pair of gnathobasic hemignaths without rami or palps, and is followed by two jaw-bearing somites (maxillary and labial).
Recent investigations (Folsom, 4) show the existence in the embryo of a prae-maxillary or supra-lingual somite which is suppressed during development.
The facial portion of the skull is very short; a long process of the maxillary bone descends from the anterior part of the zygomatic arch; and the ascending ramus of the mandible is remarkably high.
It may be supposed to have approximated, in general form, to A pus, with an elongated body composed of numerous similar somites and terminating in a caudal furca; with the post-oral appendages all similar and all bearing gnathobasic processes; and with a carapace originating as a shell-fold from the maxillary somite.
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.
In the Decapoda, where the antennal gland alone is well-developed in the adult, the maxillary gland sometimes precedes it in the larva.
In the Branchiopoda the maxillary gland is lodged in the thickness of the shell-fold (when this is present), and, from this circumstance, it often receives the somewhat misleading name of " shell-gland."
Mxp, Maxillary palp. 1, Ligula or "tongue."
The teeth form a complete series in the under jaw, and in the upper jaw on the premaxillary and maxillary bones.