38 THE NAUTILUS. 



characterized by a regularly fusiform outline, eight whorls, fine spiral 

 sculpture, slight concavity near the suture, slight convexity of the 

 anterior part of the upper whorls, the obtuse shoulder thus formed 

 being below the middle of each whorl and sometimes ornamented 

 with inconspicuous nodes. Plate II, fig. 1, illustrates Gabb's type, 

 found in the pleistocene of Santa Barbara. It is the property of the 

 University of California. Fig. 3 shows an example close to type. 

 It was dredged in about 100 fathoms, off Santa Catalina Island. 

 Length 80 mm. In fig. 2 the nodes are distinguishable, which when 

 better developed are a diagnostic feature of the next species. 

 Length 54 mm. 



Pleurotoma (Genota} tryoniana Gabb. 



Pleurotoma (Surcula) tryoniana Gabb, Pal. Cal., vol. 2, p. 6, pi. 1, 

 fig. 9. 



Pleistocene San Pedro (Gabb); Santa Barbara and San Pedro 

 (Cooper); Santa Monica (Rivers). 



Living San Diego (Cooper); San Pedro (Oldroyd). 



Typically the angular, nodose whorls, eight in number, separate 

 this species from Genota carpenteriana, but intermediate forms like the 

 example shown in fig. 2 are found rarely, and indicate the close alli- 

 ance of the two species. Plate II, fig 7, illustrates Gabb's type, 

 found in the pleistocene of San Pedro. Fig. 8 represents a specimen 

 found at Santa Monica. Its length is 62 mm. 



Pleurotoma (Genota) cooperi Arnold. Mem. Cal. Acad. Sci., Vol. 

 Ill, p. 203, pi. vii, fig. 3. 



Pleistocene. San Pedro (Arnold); Santa Monica (Rivers). 



Characterized by the angular whorls, seven or eight in number, 

 decidedly concave above the nodose angle, with relatively sharp 

 sculpture. The nodes are more numerous than in the last species 

 and become less prominent toward the aperture. Aperture less than 

 waif the length of the shell. Plate II, fig. 10, illustrates the single 

 specimen found in the pleistocene of Santa Monica. 



Pleurotoma (Genota} stearnsiana Raymond. NAUTILUS, Vol. 

 XVIII, p. 1. 



Living. San Diego and Santa Catalina Island, 25 to 40 fathoms 

 (Raymond). 



