Memoirs of the Connecticut Academy of Arts & Sciences, Volúmenes6-7Archon Books, 1919 |
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Términos y frases comunes
66 width alimentary canal angle animal antennæ antennules appendifers Apus attached axial lobe backward Barosaurus Barosaurus lentus Barrande basipodite beneath biramous bone Brachiosaurus Branchiopoda Calymene caudal centrum cephalic appendages cephalon Ceraurus cervical chilopods compound eyes coxopodites Crustacea Cryptolithus dactylopodite developed diapophyses Diplodocus carnegiei distal end dites dorsal test endobases endopodites epipodites eurypterids exopodites eye-lines figure flattened front furrows genal cæca genera genus Geol glabella gnathites gnathobases height hypostoma indicate Isopoda Isotelus Jour lamina lateral length limbs Limulus maxillæ median Middle Cambrian mouth muscles Museum Naraoia Neolenus neural spine number of segments ocelli Ordovician organs pairs of appendages parietal eye photograph plate pleural lobes position posterior end preserved prezygapophyses prezygapophysis primitive probably Professor Beecher protaspis Ptychoparia pygidia pygidium sections setæ shaft shown Sidneyia slender slices species specimen surface swimming telson text fig thoracic segments thorax Triarthrus trilobites trunk tubercle ventral membrane ventral side vertebra Walcott
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Página 34 - Walcott ; but the characters seem to be of a more comprehensive type, approaching the general structure of the other crustacea rather than that of any special form.
Página 32 - The palpus is 9 lines in length ; the basal joint measures 3 lines, and is 2 lines broad, and somewhat triangular in form. There appear to be about seven articulations in the palpus itself, above the basal joint, marked by swellings upon its tubular stem, which is 1 line in diameter.
Página 32 - Silurian), which has been much eroded on its upper surface, leaving the hypostoma, and what appear tobe the appendages belonging to the first, second, and third somites, exposed to view, united along the median line by a longitudinal ridge. The pseudo-appendages, however, have no evidence of any articulations. But what appears to...
Página 94 - ... or that it will make any near approach to perfection. The posterior segments of the remarkable trilobite Mesonacit Vermontana are of a much more delicate character than the anterior ones, and the resemblance of the spine on the fifteenth "body-segment" of this species to the terminal spine of Olenellus proper, suggests that in the latter subgenus posterior segments of a purely membranous character may have existed, devoid of hard parts.
Página 5 - The remains on which the present description is based are from the Atlantosaurus beds of Dakota about two hundred miles farther north than this well marked horizon has hitherto been recognized." (The locality referred to as at the base of Piedmont butte about two miles east of the village of Piedmont, South Dakota.) For this statement of locality see Am. Jour. Scl. March 1899, p. 228. 223. Marsh, Othniel C. Additional...
Página 41 - ... these notes. There does not appear to be evidence either in the specimens of Neolenus or the sections of Calymene or Ceraurus to sustain the " ball-and-socket " joint theory. Attachment of ventral limbs to dorsal test. — I inferred in 1881 that the coxopodite was attached to the ventral membrane by " a small round process projecting from the posterior surface of the large basal joint, and articulating in the ventral arch somewhat as the legs of some of the Isopods articulate with the arches...
Página 114 - This order possibly belongs to the Merostomata but it is distinctly allied to the crustaceans in such important characters as the structure of the legs and telson, and is therefore much generalized.
Página 41 - that in those longitudinal sections in which the ventral integument is most perfectly preserved it had been a thin, delicate pellicle or membrane, strengthened in each segment by a transverse arch. These arches appear as flat bands separated by a thin connecting membrane, somewhat as the arches in the ventral surface of some of the Macrouran Decapods. The finest illustrations of this structure have been found 1 American Jour.
Página 80 - ... absence of a separate crystalline structure in the lens, and the presence of the carbonaceous division line, we infer that there was no hard chitinous lens that would become a separate center of crystallization in fossilization, as in the lateral eyes of the trilobites, but one corresponding to that of the parietal eye of other crustaceans, and especially of the phyllopods, which is a lens- or pear-shaped sac, usually filled with water. The parietal eye of the trilobites is hence not at all comparable...
Página 5 - The most characteristic portions examined are the candal vertebrse, which in general form resemble those of Diplodocus. They are concave below, as in the caudals of that genus, but the sides of the centra are also deeply excavated. In the anterior caudals, this excavation extends nearly or Quite through the centra, a thin septum usually remaining. In the median caudals, a deep cavity on each side exists, as shown in figures 1 and 2, on page 86. ' On the distal caudals, the lateral cavity has nearly...