C O N C H O L O G Y. 



ftate, are very many ; the chief of them are the gryphytae 

 jOl" the foflilogills, of which theie are feveral fpecies : and 

 a very large flat kind with equal valves, found in Shot- 

 over and Heddington quarries, in Oxfordfliire. But the 

 largefl: bed that is known of fofli! oylters, is that near 

 Reading, in Berkdiire. They are entirely fhaped, and 



haV' 



) et, fince the oldell hiitories that rnention the place, give 

 an account of them', we mull fuppoi'e they have lain there 

 in the iame liate for a long. time. They extend over no 

 Jefs than iix acres of ground ; and juft above them is a 

 lar'je ifratum of a greenifh loam, which fome writers call 

 a green earth, and others a green fand. It is conipofed 

 of a crumbly marie, and a large portion of fand. Under 

 them is a thick (tratwm of chalk. Tliey all lie in a level 

 bed ; and the Itrata above the fiiells are natural, and ap- 

 pear never to have been dug through till the time of find- 

 ing the fliells. The oyfterfhells and green earth united 

 make a Itratum of about two feet thick ; and over tliis 

 there is a much thicker ftratum of a bluilh and very brittle 

 clay J but neither lias this ever been dug through, except 

 ■where the ihells are found. This is vulgarly denominated 

 f'lercj-clay, and is elteemed ufelefs. This clay-bed is about 

 a yard deep, and above it is a ttratum of fuller's earth, 

 about two feet and a half deep ; it is extremely good, 

 and is ufed by the clothiers. Over this there lies a ftra- 

 tum of a fine white land, unmixed either with the clay or 

 fuller's earth : this is near feven feet deep, and above it 

 is a ftratum of a itiff red clay, of which tiles are made. 

 This is again covered with a little vegetable mould j the 

 depth, however, of this llratum of tile-clay cannot be af- 

 certained, on account of the unevennefs of the hill. Thefe 



n 



recent with the foflil kinds, and defines them to be fliells 

 with unequal valves, one valve being flattilh, the other 

 convex, the beak peiforated, and tlie hinge inarticuhitc 

 or toothlets. However, he miltook fome fpecies ; for he 

 propofed the gryphites, which, by all its charaflers, is a 

 true oylter, and the pellucid or glafs Chinefe oyfter, im- 



e the fame fubllance with the recent oyfter-thells; and properly fo called, as fpecies of anomia;. Davila treats 



,-^..., ij.,1 i_-,i. ._• ._ ^u_. _- :._ .1 1 _:..- this clafs fyftematically, and as a gciius of his firll family 



of oylters. He detines them as fliells whole beak or top 

 of the under valve is perforated, and riles curved up on 

 the upper valve. He does not, however, particularize 

 any charadters of the hinge, though he gives an excellent 

 figure of the inner ftructure, or appendices. Ke defcribes 

 them in the following manner: the hinge of the under 

 valve is compoled of two liiiall hooks, which are taken in 

 or hinged into the linufes or cavities of the upper valve ; 

 and it has two interior appendages fixed towards the top 

 of the upper valve : this ltru.iture he obferved ip two fpe- 

 cies. In another fpecies, the hinge was nearly the fame, 

 but had two long and narrow fide appendages proceed- 

 ing from the lop of the upper valve, which extend them- 

 felves to the middle of it, where they are bound or flopped 

 by two fni^U ligaments, and then return again towards 

 the top, in a very remarkable and curious manner. And 

 a third fort, (which is that of Gualtieri,) has an interior 

 appeiid.ige, lomewhat like a perpendicular gutter or pipe, 

 fixed at the top, and running down to the middle of the 

 upper valve. 



Da Cofta defines the anomise as follows, bival"es with 

 unequal valves and never eared, the beak of the largtft 

 or under valve is greatly produced, and rifes or curves 

 over the beak of the fmaller or upper valve, and is perfo- 



oylters are occafionally found whole, but moil frequently rated or pierced through li-ke a tube, from which particu 



in fingle (hells. When they are in pairs, there is gene 

 rally fome of the green fand found within them : they 

 feldom flick very faft; together ; ib that, unlefs very care- 

 fully taken up, it is not eafy to preisrve them in pairs. 



ANOMIA. — The fourth and lafl family in the divilion 

 of fhells with unequal valves, and that (hut clofe, is the 

 anomias. This faihily has long been known follil, and 

 contains a great number of fpecies, all oi which, except 

 three or four, remain yet undifcovered in a living (late ; 

 and even the few known are difcoveries made within the 

 lall forty years. Columna firll mentioned fome foilil fpe- 

 cies, and he being convinced that all folfil (hells were real 

 exuvia; or fpoils of animals, and not finding thefe de- 

 fcribed or noticed by conchologilts as fliells, called them 

 conclias rariores anomia;; which word anomia has fince 

 been fo generally ufed for them, that it is now become 

 the univerfal and eflablillied name of the family. 



Columna defcribed and figured fome foffil kinds. Lifter 

 lias alfD figured feveral in his Appendix de Conchitis to 

 Jiis Hilloria Conchyliorum ; but no recent kind being 

 dilcovered fo early, is the reafon that neither he, Buo- 

 nanni, Rumphius, nor other early authors, h.ave taken 

 any notice ot them. Dr. Woodward was the firll who ar- 

 ranged the anoniice from the foftil fhells. He kept the 

 eltablifhed name, and ranked them with fliells of unequal 

 valves, and not eared; and fuither defined them to have 

 both valves conve.x, and one of them beaked. He then 



lar they have all'o obtained the name of terebroiulce. The 

 hinge is inarticulate or toothlef*, and they have always a 

 remarkable interior llruiluie. Yet, by what obfei vations 

 can be made, fome of the foflil kinds have an evident 

 multarticulate or many-toothed hinge. It feems there- 

 fore, that the valves of the anomia; are conneiled together 

 in two ways, indead of being only inarticulate, viz. i. 

 By an inarticulate hinge ; and, i. By a multarticulate 

 hinge. The firll fet have no teeth or joints on the hinge ; 

 but the fjnaller or upper valve is always indented intj a 

 wide finus, or opening of the larger or under valve, \\\ 

 which it plays like a joint, when the exigencies of the 

 animal require opening or fliutting. The fecond fet 

 have a vilible and regular multarticulate hinge ; exaflly 

 like thatof the Noah's arks, or the multarticulate cockles. 

 On a due confideration of the deep grooves, the in- 

 dentings, the undulated margins, and other dillortions, of 

 thefe fliells, more than in any other genera, and by the 

 beak, which is perforated or tubular quite within, it 

 would appear that thele animals feldom open their fliells, 

 as moft others do, to take their food ; but noiirilh theni- 

 felves tiirough the tube or perforated beak only. By ob- 

 feivadons made on the few livifig fpecies lately difcover- 

 ed, this opinion Hands in fome meafure confirmed; as 

 the living anomix have all been found lurking in the 

 nonks between the branchings of corals, or cavities of 

 rocks. They lie therein lifted upon their flat furfaces 



arranged them into fmooth, flriated, and fulcated, each of horizontally, without any prop or folid body to reft on. 



which articles has feveral neceflary fubdivifions. Wood- 

 ward had only fothl fliells to infpefl:, confequently lie 

 could not accurately define their peculiar interior ftruc- 

 ture, or their hinge : his definition, however, is very jiiil, 

 except that he makes both fliells convex, which is nut ib 

 in feveral fpecies. 



but are upheld or fuftained only by a llrong atlhefion of 

 their tubes or perforated beaks to the fides of the cavi- 

 ties, as it in tne a£lion of lucking ; and this pofition is 

 the general one of the recent kinds. It appears likewife 

 that the hole in the beak of the conchas anomise is for the 

 purpofe of tranlmitting a llrong ligament or grillly fuh- 



Gualtieri, who figures three recent kinds, has made a fiance, by which they adhere firmly to the rocks, cor il 



particular genus for them, and calls it terehraiula. He &c. in the fame manner as that clafs of fliells commonly 



defines them, very erroneoully, as fliells with equal valves, called bears paws ; at leaft fome fpecies of them have an 



and diffimiiar fules, of a peculiar flrudlure, for inliead of opening between the two valves on one fide the hinge, 



a beak it has a perforation, and alio has a very fingular through which pafles, from the infide ofthe fhells, a. 



articulation or conne6lion within-fide. Linnasus, to efta- llrong ligament, whereby the rilh adheres firmly to any 



biilh his uf'ual precihon, poffefied fbnie of the living ihells, 

 and made them his genus 314 anomia, He has mixed the 



contiguous body. The interior llrucHure of one of the 

 living kinds feeins alio not at all particularly adapted 



t«' 



