Studies in Evolution: Mainly Reprints of Occasional Papers Selected from the Publications of the Laboratory of Invertebrate Paleontology, Peabody Museum, Yale University |
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Studies in Evolution: Mainly Reprints of Occasional Papers Selected From the ... Charles Emerson Beecher No preview available - 2018 |
Common terms and phrases
Acidaspis adult Agnostus Ampyx Angelin animal annulations antennæ appendages axis Barrande beak become belonging Brachiopoda Cambrian cardinal cephalic cephalon characters Cheirurus Cistella condition corallites Corda Crustacea Dalmanites deltidial plates Devonian differentiation dorsal dorsal valve early embryonic evidence eye-line eyes figs FIGURE fixed-cheeks foramen fossil free-cheeks genal angles genera genus Geol glabella grooved groups growth force Hall Harpes head horns hypostoma individual Jour lamellæ larvæ larval form larval stages later length limbs lobes loop lophophore Magellania margin maturity maxillæ median ment nauplius neanic nepionic stages Olenellus ontogeny Opisthoparia Orbiculoidea Ordovician organs Outline profile pair Paradoxides pedicle phylogeny pleura plications portion posterior present primitive Proëtus protaspis stage protegulum Ptychoparia pygidium represented Rept Salter septum shell showing shown side Silurian sinus species specimens spiniform spinose stages of growth structure surface suture Terebratulina thoracic segments tion Triarthrus trilobites Trinucleus variation ventral ventral valve Walcott
Popular passages
Page 289 - Terebratellidae, the acceleration of the period of reproduction, by the influence of environment, threw off genera which did not go through the complete series of metamorphoses, but are otherwise fully adult, and even may show reversional tendencies due to old age ; so that nearly every stage passed through by the higher genera has a fixed representative in a lower genus. Moreover, the lower genera are not merely equivalent to, or in exact parallelism with the early stages of the higher, but they...
Page 190 - ... and 3 pairs of biramose oral limbs, which already served to some extent for taking food. From the posterior cephalic region proceeded an integumental fold which, as dorsal shield, covered a larger or smaller portion of the trunk. The trunk segments were each provided with one pair of biramose limbs. Besides the median eye there were 2 frontal sensory organs. The nervous system consisted of brain, cesophageal commissures and segmented ventral chord, with a double ganglion for each segment and...
Page 304 - Ismenia (representing an ismeniform type of structure in the higher genera), the gwyniform and cistelliform stages are larval, and the platidiform represents an adolescent condition. Similar comparisons may be made in the other genera. Progressively through each series, the adult structure of any genus forms the last immature stage of the next higher, until the highest member in its ontogeny represents serially, in its stages of growth, all the adult structures, with the larval and immature stages...
Page 65 - Pipe-fish Phyllopteryx, previously mentioned under the head of spines for protection, shows the mimicry of a plant by an animal to a striking degree. This fish closely imitates a seaweed (figure 49) and Giinther" gives the following description of the spines and filaments on the species Phyllopteryx eques : " There is a pair of small spines behind the middle of the upper edge of the snout, a pair of minute barbels at the chin, and a pair of long appendages in the middle of the lower part of the head....
Page 94 - Edward Lambert, born in 1707, was remarkable for a most unusual and monstrous formation of the skin. His whole body was covered with a horny substance, about an inch thick, which rose in the form of numerous thorn-shaped and scale-like processes, more than an inch long. This monstrous formation of the outer skin, or epidermis, was transmitted by Lambert to his sons and grandsons, but not to his granddaughters. The transmission in this instance remained in the male line, as is often the case.
Page 288 - The first two stages in both sub-families are related in the same manner to (hcynia and Cistella. The subsequent stages are different except the last two, so that the Magellania structure is similar in all respects to the Dallina structure, and Terebratella is like Terebratalia. Therefore Magellania and Terebratella are respectively the exact morphological equivalents to, or are in exact parallelism with, Dallina and Terebratalia. The stages of growth of the genera belonging to the two sub-families...
Page 396 - Report 011 the Brachiopoda of Alaska and the adjacent Shores of Northwest America. Proc. Acad. Nat. Sci. Phila., 1877, pt. ii, p. 155. shell, seem to warrant the assertion that the surface ornaments do not appear until the second or a later period is reached in the development of the shell. For the plicate species nearly the full number of plications appear simultaneously, as in Camarotœchia indianensis, 0.
Page 210 - Crustacea may be made. This cannot be done exhaustively or comprehensively at this time, and only a few points will be touched upon. The simplicity and primitiveness of the trilobite structure will first impress the student. The variable number of segments in the thorax and pygidium in the different genera shows the unstable metameric condition of the class. The head alone seems to have a permanent number of segments and appendages. Even this is not often apparent, but the constant number of five...
Page v - University, a series of volumes has been prepared by a number of the Professors and Instructors, to be issued in connection with the Bicentennial Anniversary, as a partial indication of the character of the studies in which the University teachers are engaged.
Page 233 - ... parallel and concentric, terminating abruptly at the cardinal line. In other words, no changes occur in the outlines or proportions of the shell during growth, through the nepionic and neanic stages up to and including the completed ephebic condition. The resemblance of this form to the protegulum of other brachiopods is very marked and significant, as it represents a mature type having only the common embryonal features of other genera.