WEST AMERICAN PYRAMIDELLID MOLLUSKS. 



101 



slender, rounded, reflected, the reflection giving the base an umbih- 

 cated appearance; the parietal wall covered b}?" a strong callus. 



The type and three specimens (Cat. no. 106511, U.S.N.M.) were 

 collected at Scammon Lagoon, Lower California. The type has 

 12 post-nuclear whorls and measures: Length 7.2 mm., diameter 1.9 

 mm. Cat. no. 73997, U.S.N.M., contains a specimen from San Diego. 

 Three have been determined for Mrs. Oldroyd from San Pedro and 

 two for Doctor Arnold from Scammon Lagoon. 



TURBONILLA (PYRGISCUS) CASTANEA Keep. 



Plate 9, figs. 1, la. 

 Chemnitzia. castanea (Carpenter,) Keep, West Coast Shells, 1888, p. 52, fig. 33. 



Shell elongate-conic, chestnut brown. Nuclear whorls very small, 

 two and one-half, depressed, helicoid, having their axis at right angles 

 to that of the succeeding turns, in the first of which they are about 

 one-fourth immersed. Post-nuclear whorls flattened in the middle, 

 slightly excurved at the summit, where they are faintly shouldered 

 and somewhat contracted at the periphery, marked by rather ir- 

 regular, strong, low, rounded, retractive axial ribs; of which 20 occur 

 on the third, 22 on the fourth, 24 on the fifth to seventh, 26 on the 

 eighth, 2S on the ninth, and about 50 upon the penultimate whorl; 

 upon this they are very irregular. Intercostal spaces less wide than 

 the ribs, shallow, marked by a series of spiral pits, which vary in 

 width and number on the various whorls; on the early ones there are 

 eight, on the ninth there are twelve, while on the penultimate there 

 are sixteen between the peripheral series and the summit. Sutures 

 well marked. Periphery and base of last whorl inflated, marked by 

 the continuations of the axial ribs, which extend almost undi- 

 minished to the umbilical area; and about twenty subequal and sub- 

 equally spaced incised spiral lines. Aperture pear-shaped; posterior 

 angle acute; outer lip thin, showing the external sculpture within; 

 chestnut brown; columella slender, strongly curved, and slightly 

 revolute; parietal wall covered by a thick callus. 



The specimen described and figured (Cat. no. 160224, U.S.N.M.) 

 was collected by Mrs. Oldroyd at San Pedro, California. It has eleven 

 post-nuclear whorls and measures: Length 10.5 mm., diameter 2.5 mm. 

 Professor Keep's ty])es which we have had for examination came 

 from San Diego. 



The following specimens have been exaniined: 



2565— Bull. 68—09 8 



