405 



POLYPES 



POLYPIFERA. 



406 



The following descriptions and cuts will give some idea of the 

 forms of this genus. 



A', rostrata. Shell transverse, oblong, rather convex, thin, tranaverely 

 striated ; anterior side longest, attenuated and rostrated. 



yucula rostrata. 



N. margaritacca. Shell obliquely ovate, trigonal, rather smooth ; 

 cardinal teeth straight, acute ; margin crenulated. 



Xuatla margaritacta. 



1 , Interior of Valve, showing the teeth on each aide of the hinge, and the car. 

 tilaginons pit in the centre. 2, Exterior of Valve. 3, View of the Teeth, the 

 dorsal margin of the >hell being towards the observer, enlarged. 4, Valves 

 closed, showing the umboncs. 



Trigonia is most frequently referred to the family Trigonida. 



[TRIGONIDJ3.] 



POLYPES. [POLIPIKERA.] 



POLYPHY'LLIA. [MADBEPHYLLKEA.] 



POLYPHYSA (Lamouroux), a little-known genus of Corallines. 



POLYPIARIA. [POLTPIFEBA.] 



POLYPIFERA, POLYPIARIA, or POLYPI, an order of Radiate 

 Animals, thus characterised by M. Milne-Edwards : Animals organised 

 for a sedentary mode of life, having no locomotive organs, and being 

 provided with a circle of retractile tentaculae around the mouth, and a 

 central gastric cavity, not communicating with an anus, and containing 

 the reproductive organs when these exist, in general fissiparous, or 

 multiplying by buds as well as by ovules. 



Our knowledge of the forms and functions of this group of animals 

 is comparatively recent. The discoveries of Trembley regarding the 

 structure and animal functions of the Phytoid JJydne, and Plumatellte 

 of fresh-water, opened a new field of research into the nature and 

 relations of many neglected forms of life, and gave occasion for much 

 correct inference and baseless conjecture. [HYDRA.] Borrowing from 

 Aristotle and Pliny the term ' Polypus,' by them applied to a cepha- 

 lopod, the systematic naturalists who followed Linnaeus collected under 

 this title many really animalised masses in the form of plants, and 

 after abundant examiuations by Ellis and others of the membranous, 

 horny, or stony ' fulcra," bases or axes, which remain after desiccation 

 or decay of the softer parts, generally agreed in opinion that to all 

 these plant-like bodies were associated active living animals like the 

 Hydras described by Trembley. 



As in a tree the flowering and reproductive organs manifest more 

 active and varied functions than tbe general mass of bark and wood 

 which serves to unite them in one common life, so in these Zoophyta 

 the little Polypi expanding from their cells for food, light, or aeration, 

 and shrinking back upon the agitation of the water, or withdrawal of 

 the light, seemed like so many animal flowers, which might be studied 

 apart from the Polypiaria which they adorned. They were in fact 

 studied apart, and unfortunately attention was more directed to the 

 wonderful permanent fabric, or Polypidom, as Lamouroux calls it, 

 than to the Polypi themselves. Hence the imperfection of all the 

 schemes of classification for this portion of the Zoophytic division of 

 the animal kingdom, and many of the erroneous generalisations and 

 hypotheses regarding the lower forms of animal life. There was 

 besides a real impediment in the way of accurate and satisfactory 

 observation of these minute parts of creation in the imperfection of 

 microscopes. 



Lamarck was the first who attempted to classify these creatures in 

 the following way : 



Polypi Ciliali, as many of the Rotiferous Infusoria. 



Polypi Denudati, as the Hydra. 



Polyfii Vaginati, as the compound Sertularia, Corals, &c. 



Polypi Tubifcri, as the Lobularia and its allies. 



Polypi Natantet, as the PennatiUaricc. 



The Actinia, thus expressly excluded from the class of Polypi, are 

 very closely related to them. 



l)r. Johnston, in his ' British Zoophytes,' gives the following classifi- 

 cation of these animals : 



Sub-Claw 1. Radiated Zoophyta. 'Body contractile in every part, 

 symmetrical ; alimentary canal with one opening ; gemmiparous and 

 oviparous. 



Order 1. Hydroida. Polypes compound; mouth with filiform 

 simple tentacula; stomach excavated in the cellular substance of the 

 body ; no distinct muscular apparatus; the body contractile in all its 



parts ; gemmiparous externally. Polypidom (if existing) external to 

 the polypes. (Hydra, Sert-ularia, &u. Nudibrachiata of Farre.) 



Order 2. Asteroida. Polypes compound ; mouth encircled with 

 eight fringed tentacula; gemmiparous internally; stomach membra- 

 nous. Polypidom an internal axis. (Gorgonia, &c.) 



Order 3. Hdianthoida. Polypes siugle ; mouth encircled by tubu- 

 lous (aquiferous ?) tentacula ; stomach membranous, plaited; oviparous 

 by internal ovaria. (Actinia, &c.) [AciiNiADJ).] 



Sub-Class 2. Molluscar Zoophyta (Polyzoa of Thompson ; CUio- 

 brachiata of Farre ; Bryozoa of Ehrenberg). Body not contractile, 

 symmetrical; mouth and anus separate; gemmiparous anoToviparous. 



Order 4. Ascidioida. Polypes aggregated ; the mouth encircled 

 with filiform ciliated tentacula; stomach distinct, intestine recurved 

 to an anus near the mouth ; ova internal. (Cellaria, &c.) 



In this work the last sub-class of Dr. Johnston ia treated of in a 

 separate article, POLYZOA, which has been written by Mr. Busk, who 

 has subjected this order of animals to a thorough examination, the 

 results of which have been given in his beautifully illustrated ' Cata- 

 logue of the Polyzoa,' in the collection of the British Museum. 



In the present article we propose to give a synopsis of the families 

 and the names of the genera of the Polypi, drawn up principally from 

 M. MUne-Edwards's ' Introduction to the British Fossil Corals," pub- 

 lished by the Palteontographical Society. 



Sub-Class I. COHALLARIA. 



Polypi possessing distinct internal reproductive organs, and having 

 the gastric or visceral cavity surrounded by vertical radiating mem- 

 brauaceous lamella;. 



Order 1. ZOANTHARIA. 



Polypi with conical, tubular, simple or arborescent but not bipin- 

 nate tentacula, and with numerous perigastric membrauaceous laminae, 

 containing the reproductive organs. 



Sub-Order 1. Zoantharia Aporosa. 



C'orallum composed essentially of lamellar deruiic sclerenchyma, 

 with the septal apparatus highly developed, completely lamellar, and 

 primitively composed of six elements ; no tabulae. 



Family 1. Turbinolidie. 



Corallum in general simple, never fissiparoua, and multiplying by 

 lateral gemmation in compound species. Interseptal loculi extending 

 from the top to the bottom of the visceral chamber, and containing 

 neither dissepiments as in the Astreidce, nor synaptieulaj as in the 

 Fungid(e. Walls thin, lamellar, and imperforated. Septa highly deve- 

 loped, simple, compact, iu general regularly granulated on each side, 

 and never denticulated or lobulated at their apex. Costfe in general 

 well marked and straight. No coonenchyma in the compound 

 polypidoms. 



First Tribe. Cyathininai. 



Calicule presenting one or more rows of pali, placed between the 

 columella and the septa. 



A. A siugle coronet of pali. 



Genera, Oyathina, Coinocyathus, Acanthocyathus, Eathycyathut, Bra- 

 cyathut, Ditcocyathus, Cyclocyathua. 



. Pali of divers orders, forming two or more coronets. 

 Gen. Trochocyathus, Leptocyathux, T/tecocyathiis, Paracyathus, ffetero- 

 cyalhui, Deltocyathus, Tropidocyathus, Placocyathus. 



Second Tribe. Twbinolinw. 



Corallum destitute of paU ; the septa extending to the columella, 

 or meeting in the centre of the visceral chamber. 



Gen. Twbirwlia, Sphenotrochuz, Platytrochui, Ceratotrochus, Disco- 

 trochut, Desmophyllum, Flabellum, Placotrochus, Blastotrochva, Rltizo- 

 trocliua. 



Aberrant Group. Paeudo-Turbinolidce. 



Corallum simple, with the loculi open and devoid of syuapticulto, 

 or dissepiments, as in Turbinolidce, but having the septa represented 

 by groups of three vertical laminae, not adhering together, excepting 

 near their external margin, where they are united by a common costa, 

 a mode of structure which is quite anormal in tho whole order of 

 Zoantharia. 



The only genus is Datmia. 



Family 2. Oculinida:. 



Corallum composite, produced by gemmation, and presenting in 

 general an abundant compact cconenchyma, or common tissue, the 

 surface of which is smooth, delicately striated near the calices, or slightly 

 granular, but never echiuulate ; walls of the corallites complete (that 

 is to eay, presenting no perforations), not distinct from the coonen- 

 chyma, and increasing by their internal surface BO as to invade pro- 

 gressively the inferior part of the visceral cavity, and to fill it up 

 more or less completely in old age. Loculi imperfectly divided by a 

 few dissepiments ; no synapticulte. Septa entire, or having their 

 upper edge slightly divided. 



1. Septa of various sizes forming distinct cycla. 



Gen. Oculina, Trymhelia, Cyathdia, Aitrkelia, Synhelia, Acrhelia, 

 Lophdia, Ampltelia, Diplhdia, Enallhelia, Axhelia, Grypthelia, Endliclia, 

 Slylatter. 



