APPENDIX III 363 



APONEUROSIS (G. apo, from, plus neuron, a sinew), a broad flat fascia or 



sheet of tissue, attaching a muscle. 

 APSIS (G. an arch), a combining form; synapse, Anapsida, Diapsida. 

 AQUA (L. water), a combining form; aqueous, acjueduct. 

 ARACH (G. a spider's web). 



ARBOREAL (L. arhor, a tree), pertaining to trees, as tree-living. 

 ARACHNOID (G. arach, plus eidos, form), the very thin, middle covering of 



the brain, between the pia and dura mater. 

 Archaeopteryx (G. archos, ancient, plus pteron, wing), a fossil bird of 



the Jurassic Period, with teeth and a reptilian tail. 

 Archegosaurus (G. archos, plus sauros, a lizard), a primitive genus of 



extinct stegocephahan amphibia. 

 ARCHENTERON (G. archos, plus entcron, gut), the embryonic digestive tract, 



formed by gastrulation. 

 Archeozoic (G. archos, ancient, plus zoon, animal), the most ancient 



sedimentary rocks, followed in succession by the Proterozoic. 

 ARCUALiA (G. arcus, a bow), the cartilaginous anlagen of the vertebrae, 



eight arcualia appearing in each segment. 

 .ARTHROS (G. a joint), a combining form; arthritis, Arthrodira. 

 Artiodactyla (G. artios, even, plus daktylos, finger, toe), an order of 



herbivorous mammals with the axis of the leg between the second 



and third digits; cows, deer, sheep, pigs, and hippopotami. 

 ARYTENOID (G. arytaiua, a funnel), a pair of laryngeal cartilages lying 



posterior to the thyroid cartilage. 

 ATLAS (G. tlao, to bear), the first cervical vertebra. 

 ATRIUM (L. entrance chamber), an outer cavity, as the atrium (auricle) 



of the heart; or the specialized outer cavity of Amphioxus or the 



tadpole. 

 ATROPHY (G. a, without, plus tre-pho, nourish), a wasting or withering of 



the body or any of its parts. 

 AURICLE (L. diminutive of auris, ear), the pinna of the ear, or the receiving 



chamber of the heart. 

 Australopithecus (L. auster, south, plus G. pithckos, ape), a fossil 



anthropoid found in Africa, with human characteristics. 

 AUTO (G. self), a prefix; autonomic, autointoxication, autostyhc. 

 AvES (L. birds), a class of vertebrates with feathers, 

 AXILLA (L. diminutive of axis), the armpit. 

 axis (L.), a line around which parts are symmetrically arranged; as the 



antero-posterior axis of the body. 

 AXONE (G. axon, axis), the efferent fiber of a nerve cell. 

 AZYGOS (G. a, without, plus zygon, a yoke), a mammalian vein homolo- 

 gous with the cardinals. Azygons (adjective), occurring singly. 



B.\LANOGLossus (G. balanos, acorn, plus glossa, tongue), a genus of marine, 



worm-like, Hemichordates; the "acorn worms". 

 BASi (L. base), a prefix, basidorsal, basioccipital. 

 Bdellostoma (G. bdellion, a variety of plant, plus stoma, mouth), a genus 



of myxinoid cyclostomes from the Pacific. 

 Bi (L. two), a prefix, biceps, bi-lobed. 



BIOS (G. life); a combining form; biology, amphibia, biogenetic. 

 BLAST (G. blasteo, to sprout), a combining form denoting formation or 



development. 



