.1914] 



Engl ish : Agasoma-like Gastropods 



251 



above the line of angulation of previous whorl; ornamented by twenty 

 spiral lines, which are usually very faint if the specimen is at all 

 eroded ; these lines crossed by numerous very fine obscure growth- 

 lines; columella with small callus, an impressed line marking the limit 

 of the mantle attachment ; mouth-opening long, narrow; canal narrow, 

 deep, curved backward. 



Height 35 mm., width 18 mm. : mouth-opening length 25 mm., 

 width 6 mm. 



This species is characteristic of the upper faunal zone (Scutella 

 breweriana zone) of the Monterey group in the region of San Pablo 

 Bay and Mount Diablo (Univ. Calif. Loc. 1. 28, 205, 1354, 1455). 



AGASOMA GRAVIDUM (Gabb) 



Plate 25, figures 7 and 8 



Clavella gravida Gabb, Palae. Calif., vol. 2. p. 4, 1869. 



Agasoma gravida Gabb, Palae. Calif., vol. 2, p. 46, pi. 1, fig. 6, 1869. 



Shell short, stout ; spire conical ; apical angle larger than on other 

 species ; spire one-third height of shell ; body-whorl roundly angu- 

 lated near the middle, the upper part having the same slope as spire ; 

 on body-whorl suture bordered by elevated shoulder or carina ; early 

 whorls have sixteen to twenty low vertical ribs which are lacking on 

 body-whorl; shell ornamented by spiral lines which are coarser and 

 of alternating widths on the anterior part of body-whorl ; along the 

 middle of body-whorl two or three of these lines are more prominent, 

 and upon them is a series of twelve to twenty evenly spaced, small 

 sharp tubercles ; mouth-opening rather wide ; outer lip simple ; callus 

 small ; canal curved. 



This species differs from A. barkerianum and its varieties in 

 smaller size, wider spire, coarser ribbing, less prominent carina, and 

 presence of sharply pointed equally spaced tubercles along middle 

 of the bod}* whorl. 



Height 24 mm., width 17 mm. ; height of spire 6 mm. ; mouth- 

 opening length 17 mm., width 9 mm. 



Characteristic of the base of the Monterey group as developed in 

 Contra Costa County (Univ. Calif. Loc. 189, 1686) ; ? Santa Cruz 

 Quadrangle (Univ. Calif. Coll.). 



