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 strise; 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 Planorbis 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 y 2 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 calif ornicus 



"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 reflects 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 



