m 



PERMCA. 



PETROMYZin.'E. 



PERSU'A. [AKTODALPS] 



PERSlCA'RlA. [PoLraonni.] 



PEBSrcoLA. [VoumDJtl 



PER8IMON. or PERSIMMON. , 



PERSPIC1LLA (Swainson). a genus of Water-Chats (FluvicoUna). 



PERSPIRATION. (SMB.] 



PKUr. I'.AI.SAM OF. [MTBomRMOM.] 



I'KlirvtAX HARK. [CIXI-HUXA; QUIXQUIXA.] 



PETAL. [COROLLA ; MOHI-UOUKJY ; FLOWER.] 



PET A LITE, a Mineral which occurs massive. Structure perfectly 

 lamellar in on* direction. Cleavage parallel to the lateral planes and 

 both diagonals of a rhombic prum. Fracture uneven. Hardness 6'5. 

 Brittle. Colour grayiah, greenish, or reddish-white. Streak white. 

 Lustre vitreous, inclining to resinous. Translucent Specific gravity 

 2-41 to 2-45. When heated in acids it undergoes partial decomposition ; 

 mite a blue phosphorescent light when gently heated. When by 

 iUelf, it melU with difficulty, and only on the edges ; but with borax 

 it fuses into a colourless glass. It occurs at Uto'n in Sweden, and 

 in North America. It consists, according to Gmelin, of 



Silica 74-17 



Alumina 17-41 



Lithia 5-16 



l.ime 0-32 



Water 2-17 



99-23 



PETASITES, a genus of Plants belonging to the natural order 

 Compontir, the sub-order TuktUijtorir, the tribe Eupatoriea, and the 

 section .4 Jaiotryfeir. Th heads are many-flowered, subdicocious ; the 

 female florets are filiform, obiquely truncate, or shortly ligulate ; iu 

 many rows in the female heads, none or in one row in the male heads. 

 The male florets tubular ; few and central in the female heads, occu- 

 pying the whole disc iu the male heads. Receptacle naked ; involucre 

 in one row. 



P. rulyarit (TtuiHago Pttatila, Smith), the Common Butter-Bur, 

 has a dense oblong thyme, with cordate unequally-toothed leaves, 

 downy beneath, and the lobes approximate. The plant is very abun- 

 dant in wet meadows and by river-sides. It has long creeping roots, 

 by means of which it is rapidly and extensively reproduced, and is a 

 great peet in moist meadows, where it delights to grow. It puts forth 

 iu flowers in April and May before its leaves. On account of its early 

 flowering the Swedish fanners plant it near their bee-hives. Dr. 

 Bibtborp found this plant in Greece, and believed it to be identical 

 with the nTi7mjt of Dioscorides. This is the specific name of the 

 plant, and comes from ' petaaus,' a broad covering for the head. This 

 plant produces the largest leaves of any in Great Britain, sometimes 

 measuring three feet broad. The Batter-Bur was at one time sup- 

 posed to be a remedy of value iu the plague, from which it has got 

 the name of Pestilent- Wort 



P. fragnuu, Fragrant Coltofoot, has a faetigiate thyrsus, radiant 

 roundish cordate unequally-toothed leaves, and downy 

 . This plant blossoms early, has a sweet scent, and has found 

 vary generally a place in gardens. It is a desirable flower where bees 

 are kept. 



PETAURUS. [MARiUPlAtA.] 



rioLK, the Leafstalk. [LEAF.] 



PETIVE'UIA (named after James Pctivcr), a genus of Plants 

 hdnnging to the natural order Petireriacecc. It has 6, 7, or 8 

 stamens ; 4 permanent styles, at length becoming spiny and reflcxed ; 

 the point is armed with spines at the apex. The species are West 

 Indian herbs, and in pastures are troublesome weeds, giving an 

 nmtlTiTir* flavour to the milk of cows which feed upon them. 



P. alt tact a, Guinea-Hen Weed, is a small bush with a disagreeable 

 odour. It bears an erect downy stem, not branched, and of a deep 

 green colour. The leaves are oblong-obovate or oblong-lanceolate, 

 acute and scabrous at the edge, glandular near the petiole, which is 

 both glandular and downy ; the stipules are small and spiny. The 

 spike* are long, slender, and drooping at the upper end. The flowers 

 are white. The juices of this plant are excessively acrid, and if a 

 small portion of it be chewed it will render the tongue as dry, rough, 

 and black as in cases of malignant fever. 



The negroes oonxider it a sudorific, and say that fumigations or 

 vapour-bath* of it will restore motion to paralysed limbs. The roots 

 are used in the West Indies as a cure for toothache. The plant is 

 rejected by moat animals as food. The Pintado alone seems fond of 

 it ; hoc* its common name, Guinea-Hen Weed. 



Martins fays /'. ttlandra, another species, is employed in Brazil, 

 nnder the name of llaiy de IMpi, in warm baths and lotions for 

 defective contractility of the muscles, or in paralysis of the limbs. 



(LtodUy, Plan Mtdira ; Burnett, Outiina of llolany.) 



PKTI VERI ACEJ5, Pttirtriatlt, a small natural order of Exogenous 

 Plant*, of which the principal genus is Petivtria. [Prmr.niA.] There 

 are 2 other genera and 10 species. 



I'KTREL. [PRCKEM.ARIDJL] 



PKTRIVOLA. II.mioriiAoiD*.] 



I'ETUIFAt TKNS,oneof the general terms by which naturalists 

 have at different times sought to designate the vast variety of plants 

 and animals whose remains are preserved in the earth. It may be 

 thus considered as an equivalent for such expressions as formed 



stones,' ' imbedded fossils,' ' organised fossil*,' ' organic remains,' &o. 

 [ORGANIC REMAINS.] 



PETROCINCLA. [MERCLIDJS.] 



PETUOICA. [SYLVIADA] 



PETROLEUM. [NAPHTHA.] 



PETROMYa [HVSTBICIDA] 



PETROMY'ZID.*, a family of Chondropterygious Fishes. These 

 fishes constitute the section Ci/cloitomi of the ' Kogne Animal,' and ore 

 distinguished by their imperfectly-developed skeleton, their want of 

 pectoral and ventral fins, combined with an eel-like form _of body. 

 The mouth is circular, consisting of a cartilaginous ring which supports 

 the lips, this ring being formed by the soldering together of the pala- 

 tine and mandibular bones. The bronchia, instead of being pectinated 

 as in most other fishes, are purse-shaped ; they ore moreover fixed, 

 and open externally by several apertures. 



From the very imperfect state of their skeleton (which consists 

 chiefly of a ribless series of cartilaginous rings), and some other pecu- 

 liarities in their structure, these fishes may be regarded as the lowest 

 of the vertebrate animals. 



The genus Prtromy^on, as now restricted, contains the fishes com- 

 monly known as Lampreys. These eel-like fishes arc of a cylindrical 

 form, compressed towards the tail, and destitute of scales : they have 

 seven bronchial openings on each side, and a small opening connected 

 with these on the upper surface of the head, situated nearly between 

 the eyes ; the mouth, or maxillary ring, is armed with strong teeth, 

 and on the inner disc there are smaller rasp-like tubercles : there are 

 moreover two longitudinal series of small teeth on the tongue, which 

 is so formed that, by its movement in the mouth, it acts as a piston, 

 and enables the animal to attach itself by suction to any foreign body. 



P, marintu, Linn., the Lamprey, is usually about two feet in length, 

 of a yellowish colour marbled with brown ; its two dorsal fins ore 

 distinctly separated ; the second one joins with the tail fin, as well as 

 a small strip which represents the anal fin. 



" The lampreys, like the sharks and rays," says Mr. Yarrell, " have 

 no swimming bladder, and being also without pectoral fins, are usually 

 seen near the bottom. To save themselves from the constant mus- 

 cular exertion which is necessary to prevent them from being carried 

 along with the current of the water, they attach themselves by the 

 mouth to stones or rocks, and were in consequence called Petromyzon, 

 or Stone-Sucker ; while the circular form of the mouth induced the 

 name Cyclostomes, or round-mouthed fishes, which was bestowed 

 upon them by M. Dumeril." 



The Lamprey is highly esteemed for the table, and is consequently 

 much sought after in the various rivers iu which it is found. Accord- 

 ing to the author just mentioned, it is rather common during the 

 spring and summer season in some of the rivers on the southern coast 

 of England, particularly the Severn ; and is found in smaller numbers 

 in several of the rivers of Scotland and Ireland about the same period 

 of the year. " In Scotland," Sir W. Jardino says, " they ascend our 

 rivers to breed about the end of June, and remain until the beginning 

 of August They are not furnished with any elongation of the jaw, 

 afforded to most of our fresh-water fishes, to form the receiving 

 furrows at this important season ; but the want is supplied by their 

 sucker-like mouth, by which they individually remove each stone. 

 Their power is immense. Stones of very large size are transported, 

 and a large furrow is soon formed. The P. marinua remains in pair*, 

 two on each spawning-place ; and while there employed retain them- 

 selves affixed by the mouth to a large stone." 



The Lamprey feeds upon soft animal substances, and often attacks 

 fishes of large size ; and fixing itself upon them, it eats the flesh by 

 means of its rasp-like teeth. 



P. Jturiotilii, the Lampern, or River Lamprey, is common in many 

 of the English rivers. "Formerly," says the author of the 'History 

 of British Fishes,' " the Lampern was considered a fish of considerable 

 importance. It was taken iu great quantities in the Thames, from 

 Battersoa Roach to Taplow Mills, and was sold to the Dutch as bait 

 for the turbot, cod, and other fisheries. Four hundred thousand have 

 been sold in one season for this purpose, at the rate of forty shillings 

 per thousand. From five pounds to eight pounds the thousand have 

 been given ; but a comparative scarcity of late years and consequent 

 increase of price has obliged the line fishermen to adopt other sub- 

 stances for bait. Formerly tho Thames alone supplied from one 

 million to twelve hundred thousand lamperns annually. They are 

 very tenacious of life, and the Dutch fishermen managed to keep them 

 alive at sea for many weeks." 



This fish is usually about a foot in length, and coloured like the 

 common eel The lip surrounding the mouth has a continuous row 

 of small points ; there ore two large teeth ou the maxillary ring ; and 

 the dorsal fius, which are elongated, are distinctly separated. 



P. PUmeri, the Fringed-Lipped Lampern, has the two dorsal fins 

 placed close together ; it is of a shorter and stouter form than the 

 Common Lampern, and may moreover be distinguished from it by 

 the lips being furnished with numerous papillae, forming a thickly-set 

 fringe. The Fringed-Lipped Lampern appears to be usually smaller 

 than the common species. It is found in the Tweed, and in some 

 of the streams iu the southern ports of Great Britain, but appears 

 to be comparatively scarce. 



The second genus of Pctromyzida is tho Mixinc of Linnteus. In 



