ARNOLD — THE PALEONTOLOGY AND STRATIGRAPHY OF SAN PEDRO. 201 



Rare in the Pliocene and lower San Pedro series at Deadman Island. The spe- 

 cimen figured on Plate IX is the type, which is from the lower San Pedro series at 

 Deadraan Island, and is now in the United States National Museum; the specimen 

 figured on Plate V is a stumpy form, which might be called variety curta. 



Pleistocene. — San Pedro (Arnold). 



Pliocene. — San Pedro (Arnold). 



165. Pleurotoma (Borsonia) dalli, sp.nov. 



Plate VI, Fig. 2. 



Shell small, fusiform; spire elevated; ape.x mammilliform; whorls eight, sharply angulated 

 a little anterior of middle; body-whorl less angulated than those of spire; posterior portion flat to 

 slightly concave, anterior portion slightly conve.x; first four whorls slightly nodose on angle; orna- 

 mentation consists of fine oblique, incremental lines which are convexly angulated posteriorly just 

 posterior to angle of whorl; suture deeply impressed, distinct; aperture elongate-elliptical; outer lip 

 thin, arcuate anteriorly; inner lip incrusted; columella slightly recurved, with one prominent plication 

 in middle of aperture; posterior sinus prominent; anterior sinus rather short. 



Dime7isions. — Long. 23.5 mm.; lat. 9 mm.; body-whorl 13 mm.; aperture, including canal, 

 10 mm.; defl. 27 degrees. 



Distinguishable by mammilliform apex, small deflection, sharply angulated, 

 smooth whorls, and plication on columella. Specimens pronounced new species by 

 Dr. Dall. 



Rare in lower San Pedro series and Pliocene at Deadman Island. The speci- 

 men figured is tiie type, which is from the lower San Pedro series at Deadman 

 Island, and is now in the United States National Museum. 



Pleistocene. — San Pedro (Arnold). 



Pliocene. — San Pedro (Arnold). 



166. Pleurotoma (Borsonia) hooveri, sp. nov. 



Plate X, Fig. 1. 



Shell small, fusiform; apex mammilliform; whorls five or six, angulated slightly anterior to 

 middle; body- whorl less angulated than those of spire; surface smooth, except for incremental lines, 

 which are oblique, and angulated convexly posteriorly a little above angle of whorl; suture deeply 

 impressed, distinct; aperture elliptical; outer lip thin, arcuate anteriorly below posterior sinus; inner 

 lip incrusted; columella incrusted, straight, with one prominent plication in middle of aperture; pos- 

 terior sinus shallow; anterior sinus short. 



Dimensions. — Long. 13 mm.; lat. 6.5 mm.; body-whorl 8.2 mm.; aperture, including canal, 

 6.5 mm.; defl. 50 degrees. 



Distinguishable from B. dallii by greatly depressed spire, fewer whorls and 

 lack of nodes on apical whorls. Pronounced a new species by Dr. Dall. 



Rare in lower San Pedro series; two found at Deadman Island. The speci- 

 men figured is the type, which is from the lower San Pedro series at Deadman 

 Island, and is now in the United States National Museum. 



Pleistocene. — San Pedro (Arnold). 



( 26 ) March 12, \WJ. 



