846 



NORTH AMERICAN INDEX FOSSILS. 



Phyletic — pertaining to a phylum or to 



a subordinate group, the members of 



which are united by common descent. 



Phyllode — in echinoids, see II., 574, 



and Fig. 1930, d, e. 

 Phylloid — leaf-shaped. 

 Phyllum — a leaf. A common termina- 

 tion of the generic names of corals. 

 Phytogeny — the life history of a group 



of organisms. 

 Phylogerontic — referring to the old age 



of an entire group. 

 Phylum — one of the primary divisions 

 of the animal or vegetable kingdoms. 

 Pierre series — middle Cretacic of Great 



Plains region. 

 Pinnate — divided, feather-like, into seg- 

 ments along both sides of a common 

 axis. 

 Pinnulate — provided with pinnules. 

 Pinnule — one of the jointed appendages 

 bordering the arms or ambulacra of 

 crinoids, blastoids or cystoids. 

 Pioche formation — lower Cambric of 



Utah. 

 Pittsford shale — lowest division of the 



Salina of New York. 

 Plankton — an organism that drifts aim- 

 lessly, without power to direct its 

 own course. 

 Plano-convex — applied to objects with 



one side fiat and the other convex. 

 Platteville limestone — middle Ordo- 



vicic of Iowa, etc. 

 Pleopod—see II., 388. 

 Pleura (plural of p I eur on)— later al 

 portions of the thoracic rings or seg- 

 ments of trilobites, insects, etc. In 

 the trilobites, each segment is divided 

 into a central portion, the axis, and 

 two lateral divisions, the pleura (see 

 Fig. 1542). 

 Pleurotomarioid — see L, 594 G. 

 Plica (plural plica) — a fold. 

 Plication — a fold or ridge. 

 Pocono sandstone — lower Mississippic 



of Appalachians. 

 Pogonip limestone — upper Cambric to 

 lower Ordovicic of Nevada. 



Point Levis beds — lower Ordovicic of 



Quebec region. 

 Polygonal — having more than four an- 

 gles. 

 Polyp — an individtial animal belonging 

 to the group of Hydrozoa, Anthozoa 

 or Bryozoa (see Figs. 31, 56). 

 Polyparium — a single colony produced 



by the union of many polyps. 

 Polypary — a single frond or stalk of a 



hydrozoon. 

 Polypite — an individual polyp of a 



colony. 

 Porcellainous — like porcelain ; hard, 



smooth and opaque. 

 Pore — a very small opening. 



Biserial pores — in echinoids, see II., 

 574, and Fig. 1921, d. For pairs 

 of pores in simple series, see Fig. 

 1920, d. 

 Pore-rhombs — clusters of pores ar- 

 ranged in rhombs, in the calyx of 

 some cystoids. 

 Poriferous — pore-bearing. 



Poriferous zone — in echinoids, see 

 interporiferous. 

 Portage beds — upper Devonic of New 



York. 

 Port Ewen beds — division of Helder- 



bergian. 

 Posterior — situated behind. In brach- 

 iopods, that portion of the shell at 

 the beak ; in pelecypods, the side with 

 the pallial sinus ; in gastropods, the 

 apex of the spire. 

 Post-palmars — all of the plates supe- 

 rior to the axillary palmars in the 

 arms of crinoids (see Fig. 1907, PP). 

 Potosi limestone — see Yellville lime- 

 stone. 

 Potsdam sandstone — uppermost Cam- 

 bric of New York province. 

 Prefix — one, or more letters or syllables 

 united with the beginning of- a word 

 to modify its meaning, as bi, mean- 

 ing two, in biserial. 

 Prehensile — adapted to seize or grasp. 

 Preoral — situated in front of the mouth. 

 Pro — a prefix meaning before ; see 

 meso. 



