Illustrations of the recent conchology of Great Britain and Ireland, with the description and localities of all the species, marine, land and fresh water

NAYADEs .J 1\IOLLUSCA. 83 a, b; Drapcrnancl, pi. 11, f. 3; Jl/!/a picloi·um, DonoYan, Brit. Sh., pi. 1 i -~; Wood, Conch. (l, -103 ¡il ¡ o f ¡ 9. •¡ . . ~ , • , • v , • , .,;.¿ , J, !JSC«, Ba/(ll'II, l urlon, :i\fan., p. 20, pi. 2, f. ¡ O. Shcll inllalccl oYal • h' 1· b . . . ' , • , mgc me su arcuatccl ; posterior s1dc hut " ?ry slightly proclucecl; umbones ro1111llcd, placed ncar to onc Sl lh i, and a lillle apart from each other · anterior muscular im1~ressio 1 '.s _small, and dccp; pallial imp.'.ession but slightly dehncd ; rns1de of a rich pcarlaccous lustre; exterior snrface of a yellowish-green, frequcntly beautifully racliated with darker green; lines of growth not dcep; basal line arcuated. Leu<>th thrce-fift hs of its hrcadlh ; thickness upwards of lwo-fifths. 0 Figs. ·1 ami 5, pi. XXXI, externa! and interna! ,·iew of the tecth. This shell is easily distinguishcd by its more regularly oval form, and smaller size, sel<lom excee<ling ¡¡n inch and a c¡uarter in lcngth. Found in the river Kennet, above Newbury. GENUS 3.-ALASMODON,-Say. Shell lhick, generally lrans\'ersely elongate, but Yariable in fonn, equimlrn, inequilateral; a little gaping posleriorly; with or withonl auricles; umbones for the mosl part rougl, ami decorticalcd, more so anteriorly ; hingc with a !amellar, blunted, lateral tooth on lhe posterior side, situate under the ligament, but destilute of one on the anterior side; a short, irregularly indented, cardinal tooth in the right valvc, which locks between the two irregularly cresled leclh in the left , ,ah•e ; ligament exterior, ami much elongated; muscular impressions large, irre- gular, frequently double, ami placed near the extremities; pallial impression deeply <lefined. l. ALASMOD0N MARGARATIFERUS, pi. XXXI, f. 1, 2; pi. XXXII, f. 13, 14, 15; an<l pi. XXX,* f. l, 2, 3, 4. Vm·iety \. Ordinary form, pi. XXXI, f. l, 2. Alasmoclon mcwgcwitifermn, Fleming, Ilrit. An., p. •117; Unio 11!a?'{Jtt1•itifen1s, Nilsson, p. 106, No. 2 ; Turlon, Conch. Dict., P· 202, pi. 16, f. 1 ; Ib., Man., p. l!), pi, 2, f.!); lb., Ilrit. Iliv., p. 2'12, pi. 16, f. l; Rossmassler, I, p. 120, pi. 4, f. 72, 73; Thompson, Ann. and i\fag. Nat. Hist., V I, p, 55; Unio mar- garitifei·a, Drapernaud, p, 132, pi. 10, f. 17, 18, l!); Pfciffer, I, P· 11G, pi. 5, f. 11 ; Unio clo11gata, · Lamarck, An. San. Vert., VI, pt. 1st, p. 70; Dmn<tris ma1-ga1·itife1·a, Leach, MSS., p. 1O; ill,,¡<t mctrgm·ilifc1'll, Miillcr, Verm., II, p. 21O, No. 39G; Montagu, Test. Brit., p. 33 ; Donovan, Brit. Sh., pi. 73; Pen- nant, Ilri t. Zool., IV, p. SO, pi, 43, f. 18; Ilrown, 'Wernerian Mem., II, p. 505; lb., Ency. Ilrit., 1st Ed., VI, p. 405; lb., Ency. Edinensis, II, p, 542. Shell transverse, oblong-ovale; hinge line considerably nrcu- alecl ; basal line concave; umbones flat, rngged, much <lecor- ticnted, and frequcntly wilh small, round perforations; an obsolete, gradually widening hollow, extends from the umbones to the base, in both valves ; anterior si<le vcry shorl, an<l rounded; post erior si<le much elongated, and pointed; surface covere<l with a brownish-black, strong epidermis; teelh of the hinge strong, thick, subconic; righl valve with a. single tooth, notche<l on both sides, which locks into a. bifurcated, notched looth in the opposite valve; muscular impressions near both extremities, ancl are deep and complicaled; pallial imprcssion vcry distinctly defined, an<l decply rrinrked towards the anterior side; interior pcarlaccous, with irregular streaks of green, and frequently bronzcd; towards the centre are from lwenty to thirly irregular, rather deep, nearly round punctures, of the size of lhc hcad of a small pin. Lcngth upwards of two inches ami a half; breaclth fil·c inchcs and a half. Found in thc ril'crs Aun ami Avon, Dc\'Onshirc; the Con- way; thc Irt, Cumberlancl; the Lune, Lancashire ; the Tay and Forth, in Scotland; the Tyrone, Ilann, allll Slaney, Jrelaud; an<l mrious othcr localitics in Ilritain ami Ireland. This shel\ is familiarly known by the name of lhe Pcarl Muscle. In a Paper 011 Pcarls in the Philosophical Transac- tions, it is mentionecl that severa! pearls of considerable Yalue hare becn procured from the Alasmodo11 11w1-cm·ilifi-"1'1tS, which ha,•e becn found in the rivers Tyrone ami Doncgal, Irelancl. Onc of them weighcd thirty-six carats, and would harn been worth .at40., bul owing to its bcing impure, it losl much of its value. Other pearls, from the same places, hm·e sold for from .f4. 10s. to .atl0. One at the last named price was boughl by Lady Glenlealy, who had it placed in a necklace, and refused .fS0. offered for il by the Dnchess of Ormond. We are told by Camelen, that Sir John I-Iawkins had a patent for fishing pearls in the river Jrt, Cumberland. There was also a great fishery for pearls in t.he river Tay, Scotlancl, which ex• t ended from Perth to Loch T ay ; and, il is said, the pearls sent from thence to Lonclon, from the year 1761 lo 1764, wcrc worth .ll0,000. slerling. Jt is nol uncommon at lhc present time lo find pearls in the Teilh and Tay, worth from :.C\. to .f2. each. · Variety 2. Ro1ssn, pi. XXXII, f. 13, 1'1, 15, ami pi, XXX,.., f. ,1. Un io R oissyi, Michaud, CompJ., p. 112, pi. l 6, f. 28; Proceedings Ilrit. Assoc. for 1838 ; Unio 11u11-cco·itiji:1·, Hoss• massler, I, pi, •1, f. 74; Forbes, Mal. J\fon., p, <1'1; Fleming, p. 417; Thompson, Ann. all(I Mag. Nat. Hist., VI, p. 5G. This variety differs from the common form in the following particulars. The shell is much longer, in proporlion lo its breadlh; il is more uniformly ovale, the leeth somewhat more elevated; the exterior covercd with very fine, transverso strire, the epidermis hlacker, and general surface more smoolh; the hinge and basal lines le,, arcuated, interior more of a reddish• blush, or flesh-colour, an<l lhe shell consi<lerably thinner tlian in the ordinary form ¡ the muscular imprcssions are smal\er, and less deep; the puncturcs are si ttiate nearer the umbones, are elongated, nnd nol <leeply sunk, being more lacrymose in their appearance. Figs. 13, 14, ami 15, pi. XXXII, are the Isle of Man variety, ami f. 4, pi, XXX,• is from the Teith. This fonn inhaLits the TciLh, at Callander, Perthshire. Forbes has found this elegant variety in the Illack river, near Kirk Ilraddcn Church, and al Castlelon, Isle of Man, where it is common. H e says "it was formerly much soughl aftcr by the inhabitants for the sake of lhe pearls, which it not unfrc• quently conlains." 11'1r. Thompson says this variety is common to severa! localities in Ireland. Vm·iety 3. M1Non, pi. xxx,• f. 2. Unio mm-cm·itifcm, mino,·, Rossmasslcr, II, J>· 21, pi. 9, f. 129 ; Nal Michaud. Shcll small, subcompresscd; valves .very thick; the cardinal teclh compressed, and small; general form likc varicty l. Sel~ dom cx.ceeding an inch and a half in lcnglh ; and thrce inches and a half in breadth.