MAZATLAN UNIVALVES 191 



of the shell ; in the young state visible within, in the adult 

 concealed, but generally traceable in the eroded surface. At 

 the junctions of the valves, close above the valve-lobes, may 

 be seen rows of large open cells, with smaller ones above, 

 somewhat resembling the parenchyma of a leaf cut across. 

 Along the sinus is another row of plates as in the margin. The 

 structure of the shell presents many points of analogy with the 

 Cirripedes : as does the animal with others of the Articulata. 

 The integument is crowded with very deciduous, hard, green 

 scales, sharply jointed, having 3 sides, of which one is corru- 

 gated, the others smooth . They are somewhat of the shape of 

 a pistachio nut. The following measurements are not perfectly 

 exact, in consequence of the curvature of the specimens. 



A broad specimen measures long. 2 '7, lat. 1'7, div. 120. 



The largest specimen 4'2, 2'2, 105. 



Sab. San Bias, under stones, Beecliey. Mazatlan ; abundant, 



but much worn ; L'pool Col. 



Tablet 883 contains 4 sp. in the usual condition. 884, 1 do. 

 very perfect. 885, 3 sp. broad form. 886, 2 sp. elongated. 

 887, 2 sp. surface eroded, displaying the inner structure. 888, 

 1 sp. with very irregular margins, and Coiiia attached. 889, 

 1 sp. obscurely trilobed. 890, 2 sp. with head valves abnor- 

 mally large, perhaps from limpets attached. 891, valves of 

 very young sp. 892, 2 sp. valves separate to shew structure. 



Tablet 893 contains an extremely young specimen, '16 in 

 length, which probably belongs to this species. The valves 

 are more strongly pustulose, and the marginal scales much 

 larger in proportion than in the adult. There is also a row of 

 hairy processes at the mantle margin, below the scales, which 

 may be connected with the gills. It has more the aspect of 

 C. lamgatus, Sow. Proc. Zool. Soc. 1832, p. 59 : Condi. III. sp. 

 30, f. 18*, which is from the same locality, and may prove to 

 be only a variety of C. articulatus. 



219. LOPHYEUS ALBOLINEATUS, Brod. fy Sow. 



Chiton albolineatus, Zool. Journ. vol. iv. p. 368. Sow. Conch. 



El. sp. 42, f. 39. Zool. Beech. Voy. p. 149, pi. 40, f. 4. Rve. 



Conch. Ic. 

 Lophyrus albolineatus, H. fy A. Ad. Gen. i. p. 470. 



This beautiful species is remarkable for the different appear- 

 ance of valves on the same specimen, which may be either 1 



