1918] Packard: Molluscan Fauna from San Francisco Bay 299 
curved riblets converging toward the median keel, crossed by curved radiating 
threads a little finer and less prominent. Anterior valve having 8 (not counting 
the posterior sutural borders) strong radiating ribs narrower than the latticed 
intervals. Posterior valve depressed, the mucro being at the posterior third. 
“Interior bluish-white. Sinus very small and narrow. Anterior valve hav- 
ing 8 slits, median 1 slit; teeth thickened outside at the edges of the slits. 
Posterior valve having a deep rounded median sinus behind (which is continued 
upward in a superficial excavation to the mucro) and a single slit on each side. 
‘*Girdle rather narrow, leathery, ‘‘dusty’’ bearing a few hairs, with a 
rounded pore at each suture. 
Length, 1144; breadth, 7 mill; divergence, 105°.’’ 
This species is reported from San Francisco Bay by Oreutt upon 
the authority of Neweomb. It was not taken by the Survey. 
Range.—Puget Sound to San Francisco Bay (Pilsbry). 
ACANTHOCHITIDAE 
Katharina Gray 
Katharina tunicata Wood 
Chiton tunicatus Wood (1815), p. 11, pl. 2, fig. 1. 
Katherina tunicata, Carpenter (1863), p. 648; Wood and Raymond (1891), 
p- 58; Pilsbry (1892-1893), p. 41, pl. 1, figs. 1-11. 
Description —This chiton was deseribed by Pilsbry (1893) in the following 
words: 
“‘Shell oblong, elevated, the valves mainly covered by the black, leathery 
girdle, a small cordate or flask-shaped area of a dark brown color, remaining 
exposed. 
““The exposed portion is about one-third the entire width of the valve; it 
is broad behind, and often hollowed out by erosion, narrowing in front like the 
neck of a flask. The surface when not eroded shows a distinct, smooth and 
shining dorsal band, the sides (which are not divided into pleura and lateral 
areas) being microscopically densely punctuate. Anterior valve densely punc- 
tuate and having a few feeble radii. Posterior valve small. 
‘*Tnterior white. Sutural plates enormously produced; the sinus very deep, 
squared and notched at the sides, exposing a projecting lobe of the extremely 
porous outer layer. Anterior valve having 7 or 8, central one slit, the insertion- 
plates extremely long, grooved outside from the short slits to the eaves. Pos- 
terior border of the black tegumentum broadly reflexed inward. Posterior valve 
elevated, vertical behind, with a broad median notch or sinus and a variable 
number (1-4) of small slits on each side.’’ 
This species was found within San Francisco County by Wood and 
Raymond. It is not among the Survey collections. 
Range—Aleutian Islands, Alaska, to Catalina Islands, California 
(Pilsbry). 
