MAZATLAN UNIVALVES 19} 
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 ,, Sete A Dib g tt oh Qe ot ek Ooe 
Hab.—San Blas, under stones, Beechey.—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, 
l sp. with very irregular margins, and Conia 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. levigatus, Sow. Proc. Zool. Soc. 1832, p. 59: Conch. Ill. sp. 
30, f. 18*, which is from the same locality, and may prove to 
be only a variety of C. articulatus. 
249. LopHyrus ALBOLINEATUS, Brod. ¥ Sow. 
Ciuton albolineatnus, Zool. Journ. vol. iv. p. 368.—Sow. Conc/ 
Ill. sp. 42, f. 39.—Zool. Beech. Voy. p. 149, pl. 40, f. 4.—Re 
Conch. Lc. 
Lophyrus albolineatus, H. & A. Ad. Gen. i. p. 470. 
This beautiful species is remarkable for the different appea 
ance of valves on the same specimen, which may be eithe 
