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

MYTILAC)U.] MOLLUSCA. i7 Gcncrally rathcr shorlcr and broallcr lhan thc formcr two varictics, lhc anterior sidc lcss indcnlcd than thc cclulis and much thinncr and more lrnns¡1arc11t b ti · ti J JI 1 1 · 1 . • . 1 o l lll lC s lC anc cp1- ( crmis, wluch 1s gcncrally of a rich ycllow or ambcr uuder which _th~ shcll is bcautifully radialed witi1 dccp pu;plc, or b~u~; rn~1dc vcry smooth ali() glossy, with thc radialions vcry <hsl1nct; thc crcnulalions under thc bcaks small. This varicty is much lcss common than the .1.lf . eclulis, and is generally mel with in the csl uary of rivcrs. Vm·it:t¿¡ 4. SunsAXA'l'ILJs, pi. XLV, f. 4, 5, 6, 7. .1.1Iytiltts subsa.wtilis, \Villiamson, Mag. Nat. Hist., VII, p. 353, f. 4S, a, b, e, d; 11fytilus a11gulat·us, Aldcr; 11Iytilus soli- tm·ius, l\fark; 11lytilus ccZ.ulis, vm·. c1·11ss11s, Brown, MSS. Shcll strong, solid, ,•ery lhick in proporlion to its length; bcaks consi<lerably clongate<l; hinge line straight, which is par- ticularly ob1·ious in the young shcll (f. 6); front seam, or union of the valvcs, undulous; colour of a grayish-bluc ; the epider- mis dull olive; young shclls dcep bistrc-brown. lnhabits thc coasts of Yorkshirc, Durham, and Northumber- land. Mr. Williamson says lhis shell "is found in large pools lcft · by the retiring tide, in groups of three or four together, firmly altached by their s"trong byssus to lhe under surface of Jarge st.ones!' He considers it a distinct species, ancl says " the cha- rncler of its habitat, combinecl with its peculiar salid form, give it as good a litle to be styled a distinct species as, if not a better one than, that of the transparent shell of thc 11!. pellu- ciclus, or the small blunted form of the shell of 111. incm·vatus, <loes these species respectively.'' I first noticed this variety, in 1810, in company with my late value<l friend Mr. Hancock, of Newcastle, at the mouth of the Tyne, below Tynemouth, adhcring to stones left dry by the tide, in small gronps; and recordcd it as a mere variety of M. ed1,lis; not being able to <letect any specilic distinction in the animals. There can be but little doubt that the five forms enumerated are only permanent varieties of the same specics. Varicty 5. INcunVATus, pi. XXVII, f. 12. 11:lytilus inczwvat-us, Pennnnt, IV, p. 111, pi. 6•!, f. 74; Mon- lagu, p. 160; l\faton and Rackett, p. 106, pi. 3, f. 7; Brown, Wernerian Mem., II, p. 515; lb., Ency. Brit., VI, p. 423; Turlon, 13iv., p. 197; Fleming, Edin. Ency., VII, p. 99, Shell strong, opaque, broader at the base, in proportion to its lcnglh, than any of the prececling varicties; posterior side much incurvated; shell for the most part. greatly inferior in size to thc other varieties, although in sorne few instances we have found them an inch and a half in lenglh. 2. MYTILUS CRENATUS, pi. XXIII, f. 1, 2. .1.11ytilus ci·cnatus, First Ed., pi. 31, f . 1, 2; Davics and vVillcox, Ann. of Phi\., August, 1825, p. 14S; lb., Zoo\. Journ., I, p. 584; Lamarck, VI, p. 120; Ency. Meth., pi. 21'7, f. 3. Shell oblong-ol'ate, subtrigonal, beaks rather obtuse; with strong, longitudinal, rounded ribs, proclucing a crcnulatccl mar- gin; slightly wrinkled transversely; coyere<l with an oli1•e epidermis, beneath which thc shell is of a recldish-violet colour; inside tinged with golden-yellow, transvcrsely streakecl with purplc, bluish at the margins, and crenulatecl. Length nearly thrce inches; breadth an inch anda quarter. u This is :m introduced spccies, ha1·ing bccn brought from India, by the ship "Wellesley," in 1816; ancl has propagated in Portsmouth 1-Iarbour, where it is now completely naturalized. GExus l3~Mon101,A~Lamarck. Shell subtrans1·erse, equivah-e, regular, oblic¡ue; form oblong, somewhat wcclge-shaped, ali(\ greatly inequilaleral; anterior siele very small, and obtuse ; posterior side rounded, :mcl closc ; an- terior margin slightly gaping, for the passage of the byssus, and forming, with the base, a linc oblique to thc dorsal one ; beaks nearly lateral; outsicle covered with a strong, horny epidermis; hinge without tceth; ligamcnt elongatecl, all(I subinterna\; two muscular impressions, the posterior one large, sublateral, elon- gatcd, and irregular, the anterior one small, ami terminal; the pallial impression irregular, and dcstitute of a sinus. l. l\fon10LA PAPUANA, pi. XXVII, f. 1, 2, 3, ,1, 5, 6. ]lfodiola papuana, First Ed., pi. 29, f. 1, 2, 3, 4, 5, G; La- marck, VI, p. 111 ; Leach, MSS., p. 11 ; 1.l/odiol<t vulgaris, Fleming, p. 412; 1llodiola mocliolus, Tnrlon, Div., p. 199, pi. 15, f. 3, young; 1llgtilus 111odiolus, Pcnnant, IV, p, 113, pi. (;6, f. 77; Montagu, p. 163; Donovan, pi. 23. Tite young shcll, pi. XXVII, f. 2, 5, 6. Mytilus cui·tus, Pennant, IV, p. 112, pi. G4, f. 7G A, young; Jlf!Jtilu~ ba,·batus, Donovan, pi. 70; Montagu, p. l 6 l. Shcll strong, cqnvcx, rounded ancl prominent, transvcrsely subovate, oblong; posterior side, or that close lo the beak, extremely short, and slightly rounded; anterior side cxtremely long, and much roun<led; basal linc slightly concave; ontside covercd with a strong, thick, purplish-black or dark brown epi- dermis, and longitudinally wrinkled; insicle smoolh, ami whitc, exhibiting pearlaceous reílcctions in somc specimens. Length at broadest si<le three inches; breadth six inchcs. The fine specimen from which our drawing was made, was clredged in the British Channel, and is in the cabinet of Wm. Nicol, Esq., Edinburgh; ancl I posscss a specimen, measuring seven inchcs in length, and three inchcs and a quarter in breadth, which was caught by a fisherman's linc, nenr the Dell Rock, coast of Forfarshire. The young shell in its first stages is frequently of a palc yellowish-white, beautifully radiatecl with pink or chestnut- brown, with transverse streaks of the same colours; as exhi- bited in our ligures 5 and 6. In a more advanced stage, it is covered wilh a strong, chestnut epidermis, having the anterior side ancl base beset with long, unequal, straggling filam<Jntary proccsses, which have becn termed a beard. This beard is merely a prolongation of the epidermis, which drops off whcn the .shell grows to about two inches. In this con<lition it is the 11!. ba1·batus of authors. Varicl!J 1. u~rnll,ICATA, pi. XXVII, f. 3, 4 . 11f!Jlil11s mnbilicatus, Pcnnant, p. 228, pi. 68; Donomn, pi. 40; Montagu, p. 164. Shell with a deep, intorted, and wrinkled depression undcr the beak. This is merely an accidental, and by no means uncommon, nriety of the shell. The 111. papuana is a deep water species, :md is firmly fixcd to the bottom by a byssus, composed of long silky filamcnts.