Abt. 11 NEW AMEEICAN MARINE MOLLUSKS — BAKTSCH 15 



axial ribs and the spiral cords are deeply impressed, rounded pits. 

 Suture strongly constricted, channeled. Periphery of the last whorl 

 marked by a rather broad channel. Base rather long, marked by 

 eight spiral cords of which the first two, near the periphery, are 

 much stronger than the rest, the others becoming successively weaker. 

 In addition to this the deep channels between the spiral cords are 

 crossed by numerous, slender, axial threads which give them a finely 

 ribbed appearance. Aperture elongate-oval; decidedly angulated 

 anteriorly; posterior angle acute; outer lip thin showing the external 

 sculpture within, and sinuous at the edge; columella twisted, pro- 

 vided with a rather oblique fold a little anterior to its insertion; 

 parietal wall covered by a rather thick callus. 



The type. Cat. No. 362446, U.S.N.M., was collected by Dr. R. H. 

 Tremper on rocks at San Clemente Island, California. It has six 

 and one-half postnuclear whorls and measures: Length 3.7 mm.; 

 diameter, 1.2 mm. 



A topotype of this species is in Doctor Tremper's collection. 



ODOSTOMIA (CHRYSALLroA) CLEMENTENSIS, new species 



Plate 3, fig. 2 



Shell very broadly conic, bluish white. Nuclear whorls decol- 

 lated. Postnuclear whorls increasing rapidly in size, marked by 

 poorly developed, axial ribs which are strongest near the summit, 

 but evanesce before reaching the periphery. Of these 20 occur upon 

 all the whorls. These ribs are a little wider than the spaces that 

 separate them. In addition to these ribs the whorls are marked by 

 five spiral cords between the summit and periphery, of which the 

 first three are narrow and of about equal width and occupy the 

 posterior half of the turns. These render the axial ribs tuberculate, 

 the tubercles being elongate, the elongation corresponding with the 

 spiral sculpture. The anterior two spiral cords are much broader. 

 The posterior of these is feebly tuberculate, while the anterior is 

 smooth. The spaces separating the spiral cords on the spire are of 

 the same width, and the spaces inclosed between the axial ribs and 

 spiral cords are narrow elongated pits, the long axes of which coin- 

 cide with the spiral sculpture. These spiral pits pass up on the 

 sides of the ribs and usually cross them. The first supraperipheral 

 incised spiral line not being interrupted by ribs forms a continuous 

 pitted element. Periphery of the last whorl well rounded, marked 

 by a narrow, deeply incised channel which is also crossed by fine 

 axial threads that render it pitted. Base well rounded, marked by 

 13 spiral cords, of which the anterior 3 are very feeble, while the 

 rest are very regular in size and spacing, becoming successively a 

 little more slender from the periphery anteriorly. The spaces that 



