454 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
S-shapea hds; end valves with radiating series of tubercles, which are sometimes scattered. Color gray- 
white to olive, irregularly marked on central areas or ridge with blackish; sometimes all blackish. 
Length, 36; breadth, 22 mm. 
Ponce Reefs, Porto Rico, one specimen. 
Chiton marmoratus Gmelin 
Chiton marmoratus Gmelin, Syst. Nat., p. 3205, 1792. 
Chiton marmoratus Pilsbry, Man., xiv, p. 158, pl.xxxiv, (igs. 72-76, 1892. 
Shell oval, rather elevated; dorsal ridge round-angular to carinate; side slopes convex or straight; 
surface smooth, polished; lateral areas a little raised. Color olive to dark brown or purple brown, 
variously marked with darker blotches and longitudinal lines; girdle blotched alternately green and 
light blue. 
Length, 56; breadth, 32 mm. 
Guanica; Aguadilla; San Juan, Porto Rico. 
Genus ACANTHOPLEURA Guilding. 
Valves exposed, beaked, generally lusterless or eroded; provided with eyes on the forward part 
of the lateral areas and the end valves; insertion plates all conspicuously pectinated outside; girdle 
thick, covered with calcareous spines. 
Acanthopleura granulata Gmelin. 
Chiton granulatus Gmelin, Syst. Nat., p. 3205, 1792. 
Acanthopleura granulata Pilsbry, Man., xiv, p.227, pi. L, 1892. 
Shell large, oblong, moderately elevated or roundly arched; valves solid, with faintly marked 
lateral areas, granulated all over; the color is generally ashy or brownish, usually darker on the ridge; 
girdle wide, composed of various-sized spines, looking like a growth of very fine lichens, ashy, blotched 
with brownish or blackish. 
Length, 65; breadth, 38 mm. 
One of the most abundant of American chitons, found on almost every rocky coast from lower 
Florida to northern South America. The valves are almost invariably eroded, even in young speci- 
mens, so that little or no sculpture can be seen. The material collected by the Fish Hawk expedition 
was taken at nearly every locality visited in Porto Rico and on the island of Culebra. 
Acanthopleura granulata var. mucronulata Shuttleworth. 
Chiton ( Acanthropleura ) mucronulatus Shuttleworth, Berner Mitth., p. 79, 1853. 
Eastern Porto Rico (Gundlach). 
Genus CERATOZONA Dali, 1882. 
Shell with strong, exposed valves. Insertion plates of anterior valve long, sharp, rough outside, 
thickened at the slits, which correspond in position to the external ribs; middle valves with similar 
propped teeth. Girdle tough, bearing peculiar hornlike spines, generally sparsely bunched at the 
sutures. 
Ceratozona rugosa Sowerby. 
Chiton rugosus (Gray) Sowerby, Conch. 111.. No. 6, fig. 49, 1841? 
Shell oblong, rather convex; surface generally eroded; green, onve, or blackish, the central 
areas whitish along the middle, flamed with blackish or green at the sides; tail valve with a broad, 
pink ray behind; lateral areas defined by a strong rounded rib, having a sculpture of irregular, wavy 
wrinkles over ribs and interval and on the sides of the center. 
Length, 40; breadth, 25 mm. 
Aguadilla, Porto Rico, two specimens. 
Genus ACANTHOCHITES Risso, 1826. 
Valves partly buried in the girdle, the exposed part consisting of a smooth or striated dorsal 
band and granulated side areas, the latter sometimes lacking; anterior valve with five symmetrically 
] daced slits; median valves with one slit on each side; posterior valve with two to several slits; girdle 
hairy to naked, but always having four bristle-bearing pores around the head valve and a series of 
pores on each side at the sutures. 
