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

76 MOLLUSCA. rMYTILACEA, concavc spines, which incre3SC in size towards the b:1Se ; about a third of the shell opposite the ligamentary sido is destitutc of ribs, but furnished with fine, obliquc strim, which extend from thc margin oí the valves till they meet the ribs; hinge side ncarly straight, but inclining slightly towards the beaks, and sometimes a liltle convex in the middlc; base gaping, somewhat rounded, and tapering towards the apex; hinge side a little longer than the other; inside smooth, somewhat dull nacrcd ; under the apex a few transverse, cartilaginous laminm. Length six inches; breadth at the base somewhat more than two and a half. Found in deep water off the Eddystonc Lighthouse, near Plymouth, and also on the Dorsetshire co3Sl, near Weymouth; at Torbay, and on thc Susscx co3Sl, 3. PINNA ELEGANS, pi. xxvr, f. 2. Púma clel{a11s, First Ed., pi. 30, f. 2; Leach, MSS., p. 10; Pinna pap91·acea, Turton, Biv., p. 224, pi. 20, f. 3. ·Shell thin, elongate<l, of a yellowish horn-colour; provided with from six to nine inequidistant, smooth, rounded ribs, emanating from tite apex, and radiating towards the b:1Se, occupying nearly the entire surface of the valves; narrow end inflated for sorne distance beyond the middle, but much com~ pressed towards thc base, which is rounded. Length six inches and a half; breadth at base nearly three inches. A deep water species, dredged by !lfr. Prideaux on the Devonshire coast, and has been found off Torbay. ÜENUS ll~DnmssENA,-Van Beneden. Shell boat.-shapecl, or mytilform; valves carinated; ligament interna], except in a little fissure in both valves externally; a rudo cardinal tooth is situate undcr the umbo in the right vnlve, which locks into a corresponding cavity in the left ,·alve ; in thc mnbonnl angle of both valves is placed a trans,·crse par- tition, for sustaining a closing musclc ; anterior marginal seam with a fissure nenr its centre, for thc passagc of thc byssus. J. DnE1ssENA roLYM0Rl'IIA, pi. XXIX, f. 4, 5, 6, 7, S, !). Dl'eissc1m pol911wrplm, Van Beneden, Ann. Sci. Nat., 1835, p. 210, pi. 8, f. l to 11; Strickland, Mag. Nat. Hist., 1838, p. 361 ; Alder, i\fog. Zoo). ancl Dot., II, p. 117 ; Tichogo11ia Chemnit:::ii, Rossmassler, I, p. 113, pl. 3, f. 6!); llfytilus pol9- mol'pl111s, Pallus, Voy. Iluss. App., p. 211 ; iJlytilus J,Volgm, Chcmnitz, XI, p. 205, f. 2028; 11!9tilus Hage11ii, Dacr, Fér. Bull. Sci. Nat., 1826, p. 140; -- ? Volgensis, Gray, Ann. Phi!., 1825. Shcll cymbiform, cxlremely ílat in front, and acutcly carinatcd bchind; umbones incurved, pointing antcriorly, turned down- wards at thc points, ami very closely pressed togethcr; anterior sidc with an clongated, cordiform groove, reaching neárly to thc centre of the vah-es, towards thc base of which is a large, wide, clongated hiatus, acule at both ends, always situatc in the right ,·alve, for the passagc of the lyssus; the eclge of the oppositc valrn being always entire; externa\ surface covered with a rather strong, olivaceous, irregularly wrinkled epidermis, with indications of ncarly obsolcte, longitudinal, divergent ribs, or clevations; beneath this thc shell is beautifully mottlcd with zigzag brown, or purplc, transverso clouds or markin"S; inside du\l whitc, with the pallial and muscular imprcssions of a purple huc, and ,·ery glossy. This specics is subjcct to grcat varicty in length aml breadth, varying from an inch and fivc-eighths to an inch in length. Some are clongated ancl narrow ; others short and broad. It inhabits the commercial docks in various parts of Great Britain, and is to be met with in most of our canals. It is common in the Dridgewater canal, and also in many places in thc canal bctwixt Manchcster alHl Hull.; and was found by my friend Mr. Stark in thc Union canal, near Edinburgh, in 1834. Thc animals are gregarious, generally found adhcring in clusters by a strong byssus. This shcll is not an aboriginal of Dritain, being a native of the Volga, thc Danube, and other continental rivers, and has been introduccd upon timbcr; but is now so gencrally diffused throughout Dritain, that it may fairly be considcred as a British shel\. GENUS 12.-MYTILUS.-Linnrous. Shell equivalve, regular, longitudinal, somewhat wcdge- shaped, with the beaks terminating in a pointed summit ; pos- terior side roundcd, and closed; base forming a continuous linc with the anterior margin, in a dircction oblique to thc hinge line; anterior margin gaping slightly in the centre, for the pas- sage of the byssus; hinge dcslitute of teeth; ligamen! marginal, greatly clongated, and 5ubintcrnal; outside covered with a strong horny epidermis; two muscular impressions, the poste- rior one largc and irregular, the anterior very small and termi- nal; pallial impression irregular, deslitute of a sinus. l. MYTJLUS EDULts, pi. XXVII, f. 11, 12, 13, 14, 15, and pi. XLV, f. 4, 5, 6, 7.-First Ed., pi. 29, f. 11, 12, 13, 14, 15. Varicty 1, pl. XXVII, f. 11. 1lfytil11s eclulis, Linné, Syst. Nat., p. 1157; Lister, Conch., pi. 362, f. 200 ; Pennant, IV, p. 11 O, pi, 63, f . 73 ; Montagu, p, 15!); Donovan, pi. 128; Lamarck, VI, p. 126; Brown, Ency. Brit., VI, p. 423; lb., Wcmerian l\fom., II, p. 515; Flen1ing, p. 411; Forbes, p. 43; Turton, Drit. Biv., p. 196; Maten and Ilackett, p. l 05 ; .llf.1¡tulus vulgaris, Da Costa, p. 216, pi. 15, f. 5. Shell longitudinal, rather strong, ob\ong; bcaks pointed, sub- acule; anterior side angulated, nearly parallel; posterior side produced; covered with a thick, smooth, dark olive-green or brownish epidermis, bcneath which the shell is white or blue, longitudinally radiated with dcep blue or purple; inside white, its margin blue. Lcngth thrce inchcs; breadth gcncrally about half its lcngth; but varying in this respect in differcnl localities. Common on most of the Dritish coasts, adhering to rocks, stoncs, :md grave), by a filamentary byssus. Va1·ict9 2. ELEGAKS, pi. XXVII, f. 14, 15. Mytilus elegans, Lcach, MSS;, p. 1 l. More elongatcd than !he former varicty, with thc posterior side less rounded; thc epidermis very glossy. Found in the mouth of the rivcr Tay, below J3roughty Ferry, in deep water. Varicty 3. PELLUCtous, pi. XXVII, f. 13. 1ll_,¡tilus ¡ielluciclus, Pcnnnnt, IV, p. 112, pi. 63, f. 75; Chcm- nitz, VIII, pi. s,1, f. 755; l\Iontagu, p. 160; Donovan, pi. 81; Maten and Hackctt, p. 107 ; Drown, Ency. Brit., VI, p. 423; lb., Wcrnerinn i\Icm., II, p. 1 115; Turton, 13rit. 13iv., p. )!)i, pi. 15, f. 1, 2; Forbcs, p. ,13,