PORCELLANA. 



PORPHYRY. 



* 



f MMf^b MM taw for U porpoM WM loo gr*^, ud eonNqtMoUy 

 tl*naoaaotur hat been siren up. 



P. (Vmarfnuu, th. Canadian Poplar, U an American species. It ha* 

 angular branches, ft comprmed petiol ; lore* roundish onto, deltoid, 

 acuminate, subcordate at the bee*, where there rt glands serrated 

 with unequal teeth, gUbrout. It attaint height of 70 or 80 fort, 

 and i found wild in the rocky diilricU of North America between 

 Canada and Virginia. 



P. momili/m, the Black Italian Poplar. Shoot* more or IBM angular : 

 hraoehe* round; petiole slender, compressed in the upper part; diio 

 deltoid, (land* at the base, subacute, serrate, glabrous; bractea- 

 glabrous; stsmnns 10; stigmas 4. It u doubtful of what country 

 thU tree l a native. It appear* to have been introduced into England 

 by Mean. Diekson, from North America. In America howerer it 

 fa called Italian Poplar, and in France Peuplier Suie. It it probably 

 a variety of an European specie* that has been introduced into 

 America. It is the most rapid-growing of all the poplars, and in this 

 eountty the timber U considered equal if not superior to that of any 

 other spade*. 



P. foligiota, the Lombardy Poplar. Leaf deltoid, wider than long, 

 emulated, glabrous, in the bud inrolutoly folded, petiole compressed. 

 This tree is readily distinguished among the species by its peculiar 

 conical eyprsea-like form, and the total absence of horizontal branches. 

 It grows to the height of 100 and 120 feet, and sometimes 150 feet. 

 It is a native of Italy on the banks of the Po, and also of Persia and 

 the Himalaya. 



P. baltami/tra, Balsam-Bearing Poplar, or Tacamahao-Tree. Leaves 

 ovate-oblong, quite smooth, with fine glandular serratures, deep-green 

 above, almost white bat smooth underneath. Sometimes two glands 

 at the apex of the petiole. Buds covered, in the spring, with an 

 abundance of ftagraut, viscid, balsamic juice. It is a native of North 

 America, Dauria, and the Altai, and attains a height of 80 feet It 

 is remarkable for its balsamic secretion, which was formerly collected 

 in Canada in shells, and under the name of Baume Focot, was sent in 

 considerable quantities to various parts of North America. 



P. 6<*Wi/o/ta, P. MenpkyUa, P. anyulata, and P. ca*dictmt, 

 American specie*, have also been cultivated in this country, and 

 dusei t a place in all collections of these plant*. 



PORCELLANA. [PORCELLAXIDJL] 



PORCELLA'NUXC, a tribe of Anomurous Cnatatta, placed by 

 M Milne-Edwards next to the Payuri, and immediately preceding 

 the section of Macrurous Decapods. 



Porceilaiut (Lam.) The general form resembling that of the 

 Jfrw/ijSJiii. Carapace ordinarily as wide as it is long, suborbicular 

 and depressed above. Front advanced above the insertion of the 

 fctt*ntff-'l*""fr, and even capable of covering them completely when 

 they are bent back, without there being, nevertheless, antennary 

 foeaeta. Eyes small and lodged in a sort of orbit, the upper wall of 

 which fa well formed, but the limit* of which are not determined 

 externally and internally except by the antenna), and whose inferior 

 border is very short and scarcely projecting : this last border is pro- 

 longed externally, and there is between the kind of crest thus formed 

 and the border of the carapace a deep furrow, from which the external 

 pondages are inserted consequently outside the 



r baailary portion is composed of three cylindrical joint*, the 

 second of which fa the gieatsst, and their terminal stem is very long. 

 M. Milne-Edwards divide* this genus into the following sections : 

 1. Sped** whose front fa entire and does not present lateral teeth. 



a. Front triangular. 

 P. richer*. Length about an inch. It inhabits the coast* of Chili. 



oa. Front straight or slightly rounded. 



P. srWpfa. Colour reddish with great white spots. Length about 

 three line*. It inhabits the coast* of Java. 



Two other spade* are recorded, one of them from the China seas : 

 the other fa P. rjrw/u, Gray, ' ZooU Mine.,' /'i,i<lia viridu, Leach. 

 I 2. Species wooes front fa divided into three or five teeth or lobes. 

 i. Hands very wide and flattened. Pincers triangular. 



JWwltoM 



a, Tall nnfoUcd. 



P. flalyckrlti. Length about seven lines. Colour brownish. It fa 

 a native of the coast* of England and France. 



M. Hand* long, narrow, and thick ; pincers slender. 



P. loHfficontii (Puidia longicomu. Leach ; Cancer lonyicornu, Pen- 

 nant, ' Brit ZooL'). Length about S lines. It is found on the coast* 

 of England and France, 



M. Milne-Edwards thinks that the division of this genus into two, 

 under the name of I'uidia, as well as Purer liana, by Dr. Leach, has 

 been effected without sufficient reason. M. Desmarest, though he 

 adopts it, shows that the former genus is established upon insufficient 

 characters; therefore M. Milne-Edwards thinks that it ought to be 

 abandoned. 



.tfiy/eo. Leach. Carapace depressed and much longer than it is wide, 

 divided into two portions by a furrow which separates the stomachal 

 from the cardial and branchial regions ; these last are dilated, and ter- 

 minated externally by a trenchant border. The front is armed with 

 a rostrum, at the base of which is seen on each side a notch which 

 represents the orbit Ocular peduncles very short and directed for- 

 wards. Internal antenna: inserted below the ocular peduncles, and 

 their very short stem bent back between those organs and the base of 

 the rostrum ; their basilar joint globular. External antenna; inserted 

 on the same line as the internal ones, in the lateral angle of the cara- 

 pace ; their peduncle composed of four joints, the first three of which 

 are extremely small, and the fourth cylindrical and more elongated. 



M. Milne-Edwards remarks that thin genus, in his opinion, 

 approaches the Porcellancc more nearly than the (iatatlie/e, next to 

 which they had been hitherto placed; but the conformation of tho 

 abdomen of the jSglea seems to him to indicate that their natural 

 position is in the section of Anomura. [GAI.ATIIEID.K] 



.K. Iterii. Length about 2 inches. It is a native of the coasts of 

 Chili. 



ifegalopi, Leach. M. Milne-Edwards observes that the small crus- 

 taceans designated by this generic name have much analogy with the 

 Qalalheida; as well as the Porccllanulit ; and if they be really animal* 

 arrived at their entire development, they would seem to establish the 

 passage between the Anomurous and Macrurous Decapods ; for their 

 abdomen, though it does not present at it* extremity five blade* 

 united into a fan-shape, as in the last, is very much developed, and 

 serves for natation. But ho is led to believe that they are only the 

 young of some anomurous crustacean ; and that, when the form has 

 been better studied, it will be erased from the list of genera which 

 compose the order of Decapods, or at least will be assigned a different 

 place and other characters. [MiMAi.ors.] 



Monolrpit, Say. M. Milne-Edwards is inclined to believe that this 

 genus ought not to be retained, and that it has only been establixhc.1 

 on young crustaceans not arrived at their complete development ; but 

 not having himself observed them, he cannot form a decisive opinion 

 on this point They appear, he adds, to have tho greatest analogy 

 with Mtgalopt and young Dromicc. The reader is referred to Mr. Say's 

 paper on the subject, in the ' Journal of the Academy of Philadelphia ;' 

 to M. Desmarest s work (' Consideration sur Ics Cnmtacea ') ; and to 

 the ' Histoire Naturelle des CrustaocV of M. Milne-Edwards. Tho 

 species recorded are both American. 



PORCE'LLIA, a genus of Fossil tloUvuea, 



PORCE'LLIO. flsoroDA.] 



PORCUPINE. [HYSTHHID.K.] 



PORE. [SKIN.] 



PORES OF PLANTS. [STOXATB*.] 



PORITES. [MADREPOR^A; POI.YPIFERA.] 



PORO'DRAQUS (De Montfort), a genus of Btlemnilet. 



PORPES8E. [CETACEA.l 



PORPHYRA. [Ala*.; LAYER.] 



POIil'IIY'lilO. [RALI.IDA] 



PORPHYIIY. A large number of rocks of igneous origin, both 

 very ancient and comparatively modern, are thus designated, yet this 

 use of the term is neither accurate nor convenient Properly speaking, 

 a particular structure is indicated by it, and not a definite rock or 

 family of rocks. 



