356 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
(Gray) Pilsbry, from Peru, but differing in the following particulars: the posterior 
ribs of the middle valves are transversely striate, not nodular, and do not serrate 
the suture; the anterior valve has thirteen rounded finely cross-striated ribs, the 
posterior has seven; this valve considerably overhangs the posterior part of the 
girdle, and the two anterior ribs are conspicuously larger and stronger than 
the five between them. The gills are prolonged, reaching the second valve. 
Perico Island, Panama Bay, collected on the reefs by the “ Albatross” party. 
U.S. N. Mus. 110,763. 
CHITON Liye. 
Chiton (Chiton), sp. indet. 
A small species of the restricted group of true chitons was obtained at Tabo- 
guilla Island, Panama Bay. It cannot be identified with any of the known species 
from this locality, but the specimens may prove to be immature, and therefore it 
seems best to leave it for the present anonymous. 
SCHNOCHITON Gray. 
LEPIDOZONA Pitspry. 
Ischnochiton ophioderma Da tt, n. sp. 
Shell blackish or brown with blackish, usually on the central areas longitudi- 
nally disposed flecks; interior dark bluish green, with an olivaceous flush under 
the mucrones; anterior and posterior valves each with ten rather deep, sharply de- 
fined, narrow slits; middle valves with one slit on each side; girdle with numerous 
large, ovate, close-set, imbricated convex scales, smaller toward the periphery; 
sutural plates large, the sinus indistinct; sculpture of the central areas minutely 
quincuncially reticulate, but to the naked eye smooth; at the margin of the 
lateral areas the lines become stronger, forming as it were a narrow sculptured 
fringe just in front of the lateral areas; the latter, as well as the whole of the 
anterior plate and the posterior area of the posterior plate, are covered with 
rounded close-set low projections resembling scales; there are no radial ribs or 
ridges on any of the valves. Lon. of shell, 12; lat., 9; alt. of median ridge, about 
2 mm. 
On the shore at Perico Island, Panama Bay. U.S. N. Mus. 110,764. 
The sculpture of this shell is quite remarkable. I do not remember seeing 
anything like it in any other Chiton. 
This and a few other species were obtained on the reefs or near the shore 
by the ‘ Albatross” party. 
