426 
EXPLANATION OF PLATES. 
FIGURE. 
43. 
44, 
47. 
48. 
49, 
50. 
51. 
52. 
53, 
Lepeta (Cryptobranchia) concentrica, Midd. Oregon. 
O, mantle-edge; P, muscle; X, intestine; 7, genital 
2 i i . 331 
and anal papilla, 
Acmea mitra, Esch. California, 
45, 46. Acmea (Collisella) spectrum 1 (Nuttall) Reeve. “Cal., 
Acmea (Collisella) variabilis, Sowb. Valparaiso, 
Scurria scurra, Lesson. W. Coast of 8. America, 
Patella cerulea, Lam. Teneriffe, 
Patella (Helcion) pectinata, Linn. Cape of Good Hope, 
Patella (Patina) pellucida, Linn. England, . 
Patella (Metoptoma) solaris, de Koninck. Carb. _Eur., 
55. Chiton olivaceus, Sowb. A, anterior, B, middle, 
C,, posterior valve, seen from outside ; D, E, F, the 
same yalves, from within; g,sinus jugali, between the 
two anterior sutural lamin; h, A, dentes, or teeth 
between the notches or slits in the lamine of inser- 
tion; 7, %, slits in lamina of insertion; /, outer end 
of line separating the area lateralis of the middle 
valve from the area centralis; m,end of the line sep- 
arating the central area of the tail-plate from the 
posterior portion; the angulation of this line in the 
‘ . 336 
56 (and 54, Plate 85). Chiton niger, Barnes. A,anterior valve, 
from above, showing the laminz of insertion and 
notches; B, the middle valve, from above; g, sinus 
jugali, in front of the jugum, or area jugali, and 
between the two sutural lamine ; 2,1, notches between 
the sutural and insertional laminz, and forming the 
ends of the line forming the anterior border of the 
lateral and posterior border of the central areas ; 
C, tail-plate; g, sinus jugali; m, end of line sepa- 
rating the areas; D, anterior valve, from within, show- 
ing teeth (A, h) and notehes of lamine of insertion ; 
#, middle valve, from within; g, jugal sinus, between 
the sutural lamine ; 2, notch, between sutural lamina 
median line of the animal forms the mucro, 
PAGE. 
. 331 
331 
. 331 
. 332 
. 333 
334 
. 335 
335 
and side-lamina of insertion, . 336 
PLATE 85. 
54. Chiton niger, Barnes. (Explanations as above), . . 336 
57. Chiton squamosus, Linn. West Indies, é . 338 
58. Chiton (Helminthochiton) Griffithii, Salter. Silurian, 
Ireland, . : . 339 
59. Chiton ’(Chonechiton ) viseticola, Ryckholt. Carb., 
Belgium, . ‘ . 339 
64-66. Chiton (Priscochiton) Canadensis Billings, Lower 
Silurian, Canada, . 339 
