KXPLANATION OF THK PLATES. 299 



FIGURE. PAGK. 



47. Sepia officinalis, Linn, rf, dorsal cartilage; pn, fin 



cartilage ; d', posterior extension of dorsal cartilage ; 

 c/?, shell. (Keferstein), • . 27 



48. Sepia Mauritiana, Quoy, oral aspect. Showing the beak, 



surrounded by the lip and buccal membrane. (Per. 



et d'Orb), 91 



49. Strombus Isabella, Lam., male, a, anus ; p, penis; x, 



thread-like posterior filament of mantle. (Kefer- 

 stein), ......... 65 



50. Mya arenaria, L. The left valve, mantle lobe and half 



the siphons removed, a, a', adductor muscles ; 6, 

 body; c, cloaca; /, foot; g, branchiae; /?,, heart; m, 

 cut edge of the mantle ; o, mouth ; s, &■', siphons ; t, 

 labial tentacles ; o, vent. The arrows indicate the 

 direction of the currents ; the four rows of dots at 

 the base of the gills are the orifices of the branchial 

 tubes, opening into the dorsal channels, . -67, 105 



5L Muscles of Modiola. (Woodward.) aa, anterior, a'a', 

 posterior adductors ; uu and j^'p', pedal muscles ; pp, 

 byssal muscles ; /, foot ; b, b^^ssus ; m, pallial line, 68 



52. Unio pictorum, L., with the right valve and mantle 



lobe removed, a, a, adductor muscles; p, p, pedal 

 muscles; x, accessory pedal muscle; u, umbo; ^, 

 ligament ; 6, branchial orifice ; r, anal opening ; /, 

 foot ; 0, mouth ; ^, palpi, .... 67,68,105 



53. Psammobia vespertina, Chemn. ?'s, respiratory siphon ; 



e«, efferent siphon ;/, foot. (Poll;, . . . .87 



54. Mya arenaria, Linn. Showing the siphon and foot. 



7 Woodward), . . .' 87 



Plate 4. 



55. Cephalic cartilage of Sepia officinalis. (Keferstein), . 27 



56. Neck cartilage of Loligo vulgaris. Dorsal face. (Kefer- 



stein), ^ 27 



57. Sepioteuthis Blainvillianus. a, subocular fold ; J, 



siphon; chs, cartilaginous button; nch, neck plate; 

 c/n', anterior end of pen. (Keferstein), , . .61 



58. Cartilaginous shell of Cirroteuthis Mulleri. (Kefer- 



stein), ........ 27, 61 



59. Chalky scales from the skin of Scseurgus titanops, 



greatly magnified. (Troschel), . . . . .12 



60. Chromatophore from the skin of Sepia officinalis. (Kefer- 



stein), . . . . . . . , . .11 



61. The same oonti'acted, . . . . . . .11 



