PEC 



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PEN 



PECTINIBRANCHIA'TA. The sixth order of 

 mollusca, in Cuvier's arrangement. 



PECTU'NCULUS. A genus of orbicular sub- 

 equilateral marine bivalves, with an arched 

 hinge ; numerous teeth, alternately in- 

 serted in a single row. Pectunculi are 

 easily recognized by their rounded or len- 

 ticular form. Muscular impressions two, 

 and strongly marked. Recent pectunculi 

 are found at depths varying from five to 

 seventeen fathoms in sandy mud and 

 sands. Fossil pectunculi are met with in 

 the London clay and calcaire grossier, and 

 in the Bognor sandstone. 



PE'DATE. (pedatus, Lat. from pes, afoot.) 

 In botany, applied to leaves in which a 

 bifid petiole connects several leaflets on 

 the inside only ; also to a peculiar kind of 

 ternate leaf, its lateral leaflet being com- 

 pounded in the fore part : the black helle- 

 bore is an example. 



PE'DICLE. (pediculus, Lat. a little foot.) 

 The support of the Lepas anatifera, and 

 its corresponding species, by which they 

 are attached to wood, &c. 



PE'DICEL. In botany, a partial flower- 

 stalk, or a subdivision of the general 

 one, each subdivision being termed a 

 pedicel. 



PEDI'GEROUS. (from pes, a foot, and gero, 

 to bear, Lat.) Having legs; thus the 

 body of the myriapod is divided into nu- 

 merous pedigerous segments. 



PEDIPA'LPI. The second family of Arach- 

 nidans. They have very large palpi ter- 

 minated by a forceps or claw. The prin- 

 cipal animals among the pedipalps are the 

 scorpions, possessing powerful organs for 

 seizing their prey, and having a tail ter- 

 minating in a deadly sting. The other 

 pedipalps are not armed with a sting. 



PE'DUM. (pedum, Lat. a shepherd's 

 crook.) A genus of marine bivalvular 

 shells found attached by a byssus to 

 rocks. It is an eared inequivalved bi- 

 valve, gaping at the lower valve, and 

 having its beaks separated : hinge tooth- 

 less ; ligament exterior ; inferior notch 

 grooved. This genus does not appear to 

 have been found fossil. 



PE'DUNCLE. (pedunculus, Lat. from pedo f 

 a splay foot.) 



1. In botany, the stalk that bears the 

 flower and fruit. 



2. In conchology, a sort of stem by which 

 the shells of the second division of lepas 

 are attached to wood, &c. 



PEDU'NCULATE. ) Attached to obj ects su ch 

 PEDU'NCULATED. \ as wood, rocks, &c., 



by a peduncle ; having a peduncle. 

 PEGMATI'TE. A name given by the French 

 mineralogists to a variety of granite com- 

 posed of granular quartz and felspar. 

 PELA'GIAN. } (pelagus, Lat. the sea.) Be- 

 PELA'GIC. $ longing to the sea. Mr. 



Lyell says, " belonging to the deep 

 sea." 



PELA'GIAN FORMATIONS. Oceanic accu- 

 mulations ; deposites by currents, or 

 from other causes, at the bottom of the 

 sea. 



PE'LIOM. (from TrtX/w/za, Gr. blueness, 

 or of a lead colour.) A blue coloured 

 mineral resembling iolite, of which it is 

 a variety. It is found in Bavaria. 



PE'JLLICLE. (from pellicula, Lat. dim. of 

 pellis, a little skin, pellicule, Fr. pelli- 

 cella, It.) A film ; a thin crust or co- 

 vering. 



In botany, a membranous or mucila- 

 ginous covering, closely adhering to the 

 outside of some seeds, so as to conceal 

 their proper surface and colour. 



PELTA'TE. (from pelta, Lat. a target.) 

 In botany, a term applied to leaves which 

 have their footstalk inserted in the middle 

 of the leaf, and not joined to the edge ; 

 the nasturtium is a familiar example. 



PE'LVIS. (pelvis, Lat. from Tri\vq, Gr. a 

 basin.) The lower part of the trunk of 

 vertebrated animals. 



PE'NCIL. A name given to the belemnite. 



PE'NNATE. ) (pennatus, Lat. from penna, a 



PE'NNATED. $ wing.) Winged ; feathered. 



PENNA'TULA. Called, commonly, the sea- 

 pen. A polypus with a calcareous axis 

 or stem, having a double set of branches 

 extending in the same plane from both 

 sides, like the vane of a quill. Penna- 

 tulse are not fixed by any attachment to 

 the ground, but float about in the waters 

 of the ocean, carried hither and thither as 

 the current may direct them. 



PE'NNIFORM. (from penna, a feather, and 

 form.) Having the form of a feather or 



r'll. In anatomy, muscles in which 

 muscular fibres pass obliquely out- 

 wards on either side from a tendinous 

 centre, are termed penniform. The rec- 

 tus femoris affords an illustration of a 

 penniform muscle. 



PENTACA'PSULAR. (from Trevre, Gr. five, 

 and capsula, Lat. a cell or capsule.) 

 Having five cavities, capsules, or cells. 



PENTA'CEROS RETICULA'TUS. A fossil 

 species of asteria, or stella marina. 



PENTA'CEROS DENTIGINO'SUS. A fossil 

 species of asteria or stella marina, found 

 in the chalk and in the London clay. 



PENTA'CRINITE. (from TreVrt, five, and 

 encrinite.) So called from the penta- 

 gonal formation of its vertebral column. 

 The fossil pentacrinus. Pentacrinites 

 abound in the lower strata of the oolite 

 formation, and especially in the lias ; but 

 disappear entirely in the uppermost for- 

 mations. From this circumstance geolo- 

 gists were disposed to limit their exis- 

 tence to certain periods, and to conclude 

 that the pentacrinite furnished the re- 



