1914] 



Martin,: New Species of Fossil Mollusca 



191 



This species resembles in general appearance Volutopsius regu- 

 laris Dall, from the Alaskan coast. It differs from the latter in the 

 following respects : shell more ventricose, larger and more convex 

 body-whorl, whorls of the spire less rounded, outer lip more arcuate, 

 and aperture broader. 



Genus Boreotrophon Fischer 

 BOEEOTROPHON FLEENERENSIS, n. sp. 

 Plate 22, figures 3a, 35, and 3c 

 Shell small, fusiform, with about seven whorls ; spire moderately 

 high ; apex subacute ; nuclear whorls defective ; whorls of the spire 

 angulated at the middle, sculptured with about thirteen axial ribs 

 and two spiral threads separated by wider interspaces ; axial ribs 

 extend from suture to suture, nodose where crossed by the spiral 

 threads, most pronounced on the angulation, almost spinose on some 

 specimens; one spiral thread occurs on the angle and the other on 

 the anterior portion ; posterior portion of the whorls flat, sloping 

 upward to the suture ; suture distinct ; body-whorl ventricose. angu- 

 lated near the posterior margin, ornamented with about fifteen axial 

 ribs and four spiral threads which give the surface a cancellated 

 appearance ; axial ribs most pronounced at the middle of the whorl ; 

 aperture elliptical ; outer lip thickened ; inner lip smooth ; canal long, 

 curved. 



Dimensions. — Length of the type specimen, canal defective, 18 

 mm. ; maximum diameter of the shell, 9 mm. ; length of the aperture, 

 6 mm. ; length of canal of cotype, 6 mm. 



Occurrence. — This species occurs abundantly in the upper portion 

 of the Wildcat Series two miles south of Centerville, Humboldt 

 County, California. University of California Locality 1859. 



There are some variations in sculpture of this species. On some 

 specimens the axial ribs are sharply raised and produce short spines 

 on the angle of the whorls. On other specimens the sculpture is 

 more reduced and not spinose. The axial ribs are in every case more 

 prominent than the spiral threads. 



In form this species resembles Boreotrophon scalarif ormis Gould, 

 but it can be readily separated from the latter by the angulation of 

 its whorls and the spiral sculpture, which is lacking on Boreotrophon 

 scalarif ormis. 



