Pulmonata
254
shells are biostratigraphically useful in local correlations of Quaternary
deep-sea sediments. --7microfossil, --7biostratigraphy and --7deep-sea sediments.
Pulmonata --7Gastropoda.
pumice excessively cellular lava, generally of the composition of rhyolite (fine
grained granite). The cellular structure results from a disruption of the
magma by expanding gas. Some pieces of pumice have enough buoyancy to
float on water and are widely distributed.
pure culture (syn. axenic culture) culture of organisms in the absence of any
other organisms; it is an uncontaminated culture.
purse seines --7nets.
putrefaction protein degradation under anaerobic conditions. Usually this proces
does not lead to an immediate liberation of all the amino nitrogen as ammonia. Some of the amino acids are converted to evil-smelling compounds,
notably the amines. In the presence of air, the amines are oxidized with the
liberation of ammonia.
P-wave (syn. primary wave, compressional wave) a type of body wave (--7seismic
wave) that involves particle motion in the direction of propagation (alternating compression and expansion, longitudinal wave). It is the fastest of the
seismic waves, traveling 5 to 7.2 km S-i in the crust and 7.8 to 8.5 km S-i in
the upper mantle. The P stands for primary; it is so named because P-waves
are the first arriving at the observation point.
pycnocline layer in which the density of the water rapidly increases with depth,
because of the presence of a halocline or a thermocline or both. --7stratification.
pycnogonida (syn. Pantopoda, sea spiders) class of the subphylum Chelicerata
(phylum Arthropoda). These animals seem to be only composed of eight long
legs and a proboscis (long sucking-snout). The rest of the body is small and
there is no distinct head. Most species are small (1 cm) and are ectoparasites,
sucking body fluids by their proboscis, especially from Cnidaria and Bryozoa. In
the deep-sea forms as large as 30 cm exist. Example: Pycnogonum.
pyranometer (syn. solarimeter) instrument quantifying the amount of solar radiation that reaches the surface of the earth.
pyrite FeS 2 , is found in large crystals which give off sparks when struck against
metal. This property gave the mineral its name. It is formed diagenetically
(--7diagenesis) under anoxic conditions from Fe (II) and sulfur which are both
254
shells are biostratigraphically useful in local correlations of Quaternary
deep-sea sediments. --7microfossil, --7biostratigraphy and --7deep-sea sediments.
Pulmonata --7Gastropoda.
pumice excessively cellular lava, generally of the composition of rhyolite (fine
grained granite). The cellular structure results from a disruption of the
magma by expanding gas. Some pieces of pumice have enough buoyancy to
float on water and are widely distributed.
pure culture (syn. axenic culture) culture of organisms in the absence of any
other organisms; it is an uncontaminated culture.
purse seines --7nets.
putrefaction protein degradation under anaerobic conditions. Usually this proces
does not lead to an immediate liberation of all the amino nitrogen as ammonia. Some of the amino acids are converted to evil-smelling compounds,
notably the amines. In the presence of air, the amines are oxidized with the
liberation of ammonia.
P-wave (syn. primary wave, compressional wave) a type of body wave (--7seismic
wave) that involves particle motion in the direction of propagation (alternating compression and expansion, longitudinal wave). It is the fastest of the
seismic waves, traveling 5 to 7.2 km S-i in the crust and 7.8 to 8.5 km S-i in
the upper mantle. The P stands for primary; it is so named because P-waves
are the first arriving at the observation point.
pycnocline layer in which the density of the water rapidly increases with depth,
because of the presence of a halocline or a thermocline or both. --7stratification.
pycnogonida (syn. Pantopoda, sea spiders) class of the subphylum Chelicerata
(phylum Arthropoda). These animals seem to be only composed of eight long
legs and a proboscis (long sucking-snout). The rest of the body is small and
there is no distinct head. Most species are small (1 cm) and are ectoparasites,
sucking body fluids by their proboscis, especially from Cnidaria and Bryozoa. In
the deep-sea forms as large as 30 cm exist. Example: Pycnogonum.
pyranometer (syn. solarimeter) instrument quantifying the amount of solar radiation that reaches the surface of the earth.
pyrite FeS 2 , is found in large crystals which give off sparks when struck against
metal. This property gave the mineral its name. It is formed diagenetically
(--7diagenesis) under anoxic conditions from Fe (II) and sulfur which are both