no. 1826. 



M0LLUSK8 OF THE GENUS RITTIUM— BARTSCH. 



389 



BITTIUM (STYLIDIUM) ESCHRICHTII MONTEREYENSE Bartsch. 



Plate 58, fig. 5. 



Bittium (Stylidium) esckrichtii montercyense Bartsch, Proc. U. S. Nat. Mus., 

 vol. 33, 1907, p. 178-179. 



This form is a southern race of B. eschrichtii. It differs from the 

 typical form in being less strongly spirally keeled, much more smooth, 

 more slender, and in every way more elegant than eschrichtii. The 

 typical form varies in color from brown to white, and is very rarely 

 spotted. In montereyense the variegated forms predominate — that is, 

 the shells are whitish mottled with rust brown. The type, Cat. No. 

 32221, U.S.N.M., has ten whorls, and measures: Length 13.8 mm., 

 diameter 5 mm. 



Specimens examined. 



Catalogue 

 No. 



104135 



i 32221 

 32211 

 32214 

 32228 

 55992 

 56443 

 56849 



202662 

 55994 



1943S7 

 32279 

 55993 



Locality. 



Cresson City, California. 



Monterey, California 



do 



.do. 



.do. 

 .do. 

 .do. 

 .do. 



Pescadero, California 



San Pedro, California 



San Diego, California 



Gulf of California 



Cape St. Lucas, Lower California. 



FOSSIL. 



Deadmans Island, California (Lower San Pedro Series). 



Number of 

 specimens. 



1 Type. 



KEY TO THE SPECIES OP THE SUBGENERA SEMIBITTIUM, LIROBITTIUM, AND THOSE OP 

 UNCERTAIN SUBGENERIC POSITION. 



Since the nuclear whorls of seven species (probably Lirobittium or Semibittium), 

 described in the pages which follow, are unknown, I have deemed it wise to embrace 

 the members of these two subgenera, as well as the seven of uncertain position, all 

 in one artificial key. 



Spiral sculpture consisting of three strong cords between the sutures, between which 

 intercalated slender cords may occur. 

 Nodulose spiral keel at the summit less strong than the other two. 



Base with two very strong sub lamellar keels interfossa. 



Base with slender spiral cords. 



Peripheral cord exposed as a smooth band in the suture catalinense . 



Peripheral cord not apparent in the sutures c. inornatum. 



Nodulose spiral keel at the summit equal to the other two. 

 Axial ribs and spiral cords comparatively weak, always narrower than the squarish 

 pits inclosed by them. 

 Junctions of axial ribs and spiral cords forming sharp cusps. 



Whorls with a strong shoulder oldroydx. 



Whorls not shouldered fetellum. 



