1918] Packard: Molluscan Fauna from San Francisco Bay 295 
End valves with the same equal sculpture, the tail valve with the mucro central 
and a little projecting. 
Girdle rusty brown or alternately blackish and white; bearing rather 
sparsely scattered white spike-like spines, sometimes having one or two at each 
suture. Length 29, breadth 13 mill.’’ 
This chiton is reported from this region by Wood and Raymond. 
It was not taken by the Survey. 
Range.—Vanecouver Island to Lower California (Orcutt). 
Trachydermon Carpenter 
Trachydermon hartwegi (Carpenter) 
Chiton hartwegti Carpenter (1855), p. 231; Pilsbry (1894a), p. 45. 
Tonicella hartwegii, Pilsbry (1892-1893), p. 45, pl. 14, figs. 81-85. 
Chaetoplema hartwegii, Wood and Raymond (1891), p. 58. 
Description—The following is Pilsbry’s description of this species: 
“*Shell oval, rather low, the dorsal ridge obtusely rounded; dull olive green, 
generally having a pair of lighter stripes on the ridge of each valve with a 
black blotch outside of the light dashes. Girdle rather narrow, dense, micro- 
seopically closely granulated. 
The tail valve is convex as a whole, but the subcentral umbo is not con- 
spicuous. The entire surface is very closely microscopically granulated, and 
bears larger wart-like granules irregularly scattered over the minute sculpture, 
these warts being much more numerous upon the lateral areas (which are 
otherwise rather ill-defined) and the terminal valves. 
The interior is of an intense blue-green color. Sutural plates rounded, leay- 
ing a wide, angular sinus. Insertion plates shorter than the eaves, blunt, the 
anterior valve having the teeth bi- or tri-lobed, the posterior valve having them 
crenulated. Slits of anterior valve 10-11; median valves 1; posterior valves 
9-12. Haves spongy. 
Gills extending forward to the front end of the foot.’’ 
This species was reported by Wood and Raymond and by Pilsbry 
from this region. Not found by the Survey. 
Range.—Vanecouver Island to Magdalena Bay (Pilsbry). 
Trachydermon raymondi Pilsbry 
Trachydermon raymondi Pilsbry (1894b), p. 46. 
Description—This species was originally described by Pilsbry (1894) as 
follows: 
““Shell longer and narrower than 7. hartwegii. Back somewhat keeled, vary- 
ing in elevation. Color (1) olivaceous green mottled with white, sometimes with 
dark lateral streaks as in hartwegii, sometimes ruddy at the ridge, or (2) uni- 
form blackish, or (3) dark brown, uniform or with whitish flecks. 
Valves rather strong, slightly beaked when unworn, the posterior (sutural) 
margin straight or slightly concave. Intermediate valves rather rounded where 
they join the girdle, scalloping the inner border of the latter; not distinctly 
divided into areas. Lateral areas hardly or not raised (the diagonal being 
indistinet) evenly sculptured with minute, equal granules. Central areas also 
evenly sculptured throughout with similar granules, slightly finer on the ridges. 
