75 
etal wall small, scarcely touching the penultimate whorl; labrum 
slightly deflected, fuscous within; umbilicus deep. Diameter 23, 
height 9 mm. 
Living: Oregon (Nuttall). British Columbia to Baja Cal. 
1011 Planorbis tumens Cpr. 
Shell rapidly swelling, horn or reddish smoke-colored; whorls 
4 or 5, with light waving strie; sutures deeply impressed; on one 
side subangulate or subcarinate near the suture, on the other 
rounded; umbilicus very deep; aperture with a sinuous edge, one 
side standing out above, flattened below, the other flattened above, 
produced below, capacious and rounded; labrum very thin. Diam- 
eter 15, height 6.5 mm. 
Living: Mazatlan, Baja California; San Francisco, Petaluma, 
and Southern California. 
1012 Planorbis tumidus Pfeiffer. 
Shell opaque, pale horn colored or smoky, densely and finely 
striated, umbilicated above, slightly concave below; whorls 5, 
convex, subcarinated on each side, rapidly increasing, separated 
by a deep suture; aperture oblique, lunate-rounded, somewhat 
kidney-shaped. Diameter 19, height 6 mm. 
Living: Texas, Los Angeles, California. Nicaragua (T. 
Brydges). Guatemala. 
1013 Plianorbis vermicularis Gould. 
Shell dome-shaped, minutely striated by growth, whorls 4, 
the last one deflected near the aperture, rounded at periphery, 
tip depressed, suture very deep, the whorls sloping toward it; 
base cup-shaped, exhibiting all the whorls. Aperture exhibiting 
a very oblique section of a cylinder; lip embracing about % the 
height of the last whorl and joined by callus. Height 1.6, diam- 
eter 5 mm. 
Living: Oregon; California; Baja California (Orcutt). 
1014 Plectodon scaber Carpenter. 
Catalina Island, California, 40-60 fms. 
1015 Pleurobranchus californicus 
“Some time since Mrs. Oldroyd sent me 2 specimens of Pleu- 
robranchus, from San Pedro, Cal., which I could not spare time to 
examine microscopically at the moment. I can now specify their 
chief diagnostic characters as follows: Animal when fresh of a 
waxen white, with a surface apparently smooth, or rather like the 
skin of an orange, not tuberculate, but, under a glass, showing 
obsolete distant pustules hardly raised above the general surface; 
body elongate-oval, the foot longer than the mantle behind. The 
gill short, its stem finely granular, not tuberculate, with 10 or 11 
alternate short vanes, the whole adnate nearly to the tip, medially 
situated, with the contiguous genital orifices just in front of its 
anterior insertion and the anus just over the posterior insertion 
between the gill and the mantle. Eyes, rhinophores, muzzle, jaws 
and teeth, as described by Fischer (Man. Conch. xvi, pp. 301-2). 
Shell rather long and narrow, subrectangular, longitudinally ob- 
soletely striate on the left side, obscurely obsoletely punctuate 
near the anterior edge, and covered with a very thin periostracum 
which refiects nacreous tinges of color. The shell itself is white 
and thin, with a small spiral nucleus; the left margin somewhat 
recurved, the central part moderately convex; the whole extends 
more than half the length of the body and measures 12 by 6.5 mm. 
This species differs from P. digueti Rochebrune in color, in the 
proportional size and number of pinnules of the gill, in having a 
larger and differently shaped shell, and in the position of the anal 
orifice. These remarks apply to the form described by Pilsbry 
anatomically; Rochebrune states that his species was scarlet 
