Clark: The San Lorenzo Series of Middle California 163 



Class GASTROPODA 

 Family Trochidae 

 Genus CALLIOSTOMA Swains 



CALLIOSTOMA LAWSONI, n. sp. 

 Plato 22, figures 14, 17 and 18 

 Type specimen 11231, Coll. Invert. Palae. Univ. Calif., loe. 331 



Shell medium in size, thin; spire acute, higher than body whorl. Whorls 

 seven or eight, angulate ; body whorl angulated at the base and again a little 

 posterior to the middle of the shell; sides of whorls, below the upper angulation, 

 fiat; on body whorl almost at right angles to the nearly fiat base. Surface above 

 the upper angle subtabulate, sloping obliquely to the suture. Sutures channeled, 

 bounded anteriorly by a fairly distinct nodose collar. Sides of whorls, including 

 tabulate areas, covered by medium narrow, nodose, spiral ribs with interspaces 

 somewhat wider than the ribs; three nodose spiral ribs, including the one on the 

 angulation and the one forming the collar next to the suture, on the subtabulate 

 portion of the body whorl and of the whorls of the spire, a small, unnodose interrib 

 being included in each interspace ; the minor spiral ribs on the tabulate areas of 

 the larger specimens become heavier and on some specimens are not easily dis- 

 tinguished from the major spiral ribs; usually only one major nodose rib is visible 

 on the sides of the whorls of the spire below the angulation, though on some speci- 

 mens the second one next to the suture may be seen; two major spiral ribs on 

 the sides of the body whorl, one about half way between the upper angulation 

 and the base, the other on the angulation at the base ; both on the sides of the 

 whorls of the spire and on the sides of the body whorl, there are minor, unnodose, 

 spiral ribs in the interspaces between the major spiral ribbing, sometimes only 

 one, sometimes two or three in each interspace ; usually the larger number is 

 found on the sides of the body whorl ; base sculptured by eight or nine granulose, 

 fairly heavy, but somewhat variable, spiral ribs. Shell imperforate; apparently 

 no callus in umbilical region, if so, very small. 



Dimensions. — Type specimen: height, 22.5 mm.; greatest width of body whorl, 

 about 25 mm.; height of spire, about 8.5 mm. 



Occurrence. — University of California localities 30, 331, 1131, 1311, etc. 



Family PYRAMIDELLIDAE 

 Genus TURBONILLA Risso 

 TUEBONILLA sp. 



An impression of a Turbonilla was found in the same piece of 

 sandstone, from which the cast of Epitonium ventricosum was ob- 

 tained, University of California locality 1165. A fairly good wax 

 cast was made of the Turbonilla ; however, it is not complete enough 

 to warrant its description as a new species, the body wliorl as well 

 as the tip of the spire being gone. The species is of the same general 



