54 THE NAUTILUS. 
divided by one curved radial groove in front of the middle of the 
area, with one or several shorter, less distinct grooves in front of it ; 
concentrically sculptured with coarse, low, irregular wrinkles, which 
make the sutural margin feebly dentate. Central areas finely and 
minutely sculptured with irregularly zigzag transverse, vermiculate 
subgranose wrinkles, which are broken into granules on the ridge, 
and are puncticulate, the outer portions of the pleura more coarsely 
wrinkled. Valve i having weak radial grooves and concentric 
wrinkles. Valve viii with central, low, mucro, the posterior 
slope somewhat concave; sculptured like the head-valve but more 
obsoletely. 
Interior rose-pink, fading to white on the sutural laminz. Sinus 
wide, notched at the bases of the sutural laminz ; eaves narrow and 
distinctly porous. Median valves with 1-1, tail valve 16 slits; teeth 
sharp, very distinctly crenulated at the inner edge. 
Girdle wide, densely clothed with scales which are weakly 
striated, and measure about one-seventh of a millim. in width, and 
imbricate inward and backward. 
Length 11, breadth 8 mm. 
Hab. St. Vincent Gulf (Bednall). 
A peculiar little species, shorter than most Australian Jschnochi- 
tons, and wrinkled much as in J. strio/atus Gray. In the individual 
before me there are creamy patches at the outer ends of valves iv, 
vy, vii and viii; on the last valve there is some olive-green variegation 
of the cream color. 
Chiton (canaliculatus var. ?) tricostalis, n. 
Allied to C. canaliculatus Q. & G. (+insculptus Ad. and stangeri 
Ry.) and ©. discolor Souv. (-+-miniaceus Cpr.), but having fewer 
radial riblets on end valves and lateral areas than the first, and more 
elevated than discolor, with projecting, more backward-hooked 
mucro on the tail valve. 
Shell oblong, elevated, acutely keeled with nearly straight side 
slopes. Color variable, either (1) uniform chrome yellow, or (2) 
olivaceous mottled finely with white, with some white patches on the 
lateral areas, the outer halves of the pleura blackish, girdle oliva- 
ceous with cream-white bars opposite the sutures. 
Median valves a trifle beaked, the posterior (sutural) margins 
nearly straight. Lateral areas well raised, having three radial 
tuberculate riblets, the middle one shortest ; tubercles rounded and 
spaced on front two ribs, closer and compressed on the posterior rib, 
