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Heads of the boid snakes Python sebae and Python molurus were dissected and the arthrology, myology and dentition studied. Living specimens of these species were observed and their feeding behavior analyzed by means of high-and regular-speed motion pictures. Camera speeds of up to 400 frames per second permitted examination of the jaw movements during the striking and seizing of prey. Motion picture studies conducted at regular speeds provided information on cranial movements during the swallowing of prey. The morphology of the head was correlated with observed movements in an attempt to analyze the functional and adaptive implications of the jaw apparatus.The cranial apparatus was discussed in terms of a linkage or kinematic chain whose constrainment and degrees of freedom were examined and compared with the jaw linkage of lizards. It was concluded that the very rigidly constrained mechanism in lizards is in remarkably sharp contrast to the very loose apparatus in snakes.Motions of various cranial bones were analyzed with particular attention given the mechanical factors involved. In full protraction the maxillae and palatines are lifted and rotated outward about a longitudinal axis. These movements are important in orienting the teeth with respect to the prey and are related to seizing and swallow in g .Feeding adaptations of snakes have possibly attracted more interest, technical and popular, than have those of any other vertebrates save birds and man. Scholarly treatments of the snake jaw apparatus were published well over a century ago (Dug&, 1827;Duvernoy, 1832;D'Alton, 1834) and stand as important contributions to the subject even to the present time. Investigations of the cranial mechanisms in snakes were continued through the early 1900's (e.g., Katheriner, '00; Hager, '06; Adams, '25; Radovanovic, '28. '35, '37), but it was largely the work of Lakjer ('26) and especially of Haas ('29, '30a, '30b, '31a, '31b) which laid the morphological foundations upon which most of the subsequent work has been based.Within recent years there has been a renewed concentration of interest on both the descriptive and functional morphology of snake jaws. Purely descriptive papers of various authors (Anthony and Sena, '50, '51; Cowan and Hick, '51; Haas, '52, '55, '62; Albright and Nelson, '59a; Kochva, '62) have contributed greatly to the knowl-J. MORPH., 118: 217-296.edge of the cranial myology of snakes. Further information has been provided through studies that included a functional approach in addition to detailed descriptions of the head muscles (Dullemeijer,'56, '59; Kochva, '58; Boltt and Ewer, '64). The work of Gans ('52, '61) and of Albright and Nelson ('59b) is functional rather than descriptive and does not furnish extensive data on muscular anatomy.Of particular note is the increasing interest in the functional and adaptive implications of snake jaws. Recent work has tended toward a more analytical approach than had been previously applied. This kind of approach was developed by Gans ('52) in an admi...

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Adaptive explanations for the temporal fenestration in reptiles are briefly reviewed. With few possible exceptions, fenestrate appeared first in the reptiles, and have seemingly evolved independently in several different phyletic lines.The several explanations for fenestration offered by previous authors include speculations that open spaces in the skull permitted bulging of the jaw-closing muscles, and that fenestrae formed in areas of reduced stress where the presence of bone would be functionally useless. The first of these does not readily apply to initial evolutionary stages; the second is more satisfactory. Certain features of muscular attachments to bones are dealt with, and their implications applied to the fenestration probleni to add another possible explanation (which need not contradict previously published suggestions).Considerations of cranial strength in tetrapod skulls led to speculations on the lack of fenestration in temnospondyls, anthracosaurs, microsaurs and cotylosaurs. Emargination of the skd1 roof in turtles is also discussed.