270 CALIFOltMA ACADEMY OF SCIKNCES. 



The species of this genus nvv distriluitcd in :ill seas. All nur \\'c<( Ainciiran 

 forms have tlie cohimcliar InM iiittTiuil and liardly to he seen witlioiil hreaking away 

 part of tlio whorls. 



'Iho niiiul)er i>f spcfios is so great, and tlicy arc so ^inidai lo oni.' anolliLr, lliaL 

 a niimher of sections, hased chiefly on the types of sciiljiimi', iiave heen found con- 

 vcnicnl in treating of Huni. ISIost of liicse sections grade into one anotlu r lliroui;li 

 peripheral species. 



Section St riiil II rlioii illd Sacco. 



Sit ioturbonilla S\CCO, I. Moll, del Piedmontc e dclla I.ij^iiria, p. 94, 1S92. 



Shell as in Chemititsia, Init very finely and closely .spirally striated on the spire and base. 



Type, Slrioturhonilla ulpina Sacco, /. c. 



284. Turbonilla (Strioturbonilla) muricata Carpenter. 



Chetntiilsia muricata Cl'R., Mazatlan Cat., Brit. Assn. Re[)t., iJi56, p. 260. 



Shell small, slender, solid, rather thin, milk-white; nuclear whorls two and one-halt, heli- 

 coid, smooth, one-third sunken, their axis being at right angles to the axis of the post-nuclear 

 whorls; post-nuclear whorls flattened, ornamented by eighteen to twenty-two very jMominent, 

 elevated, convex-topped, slightly oblique a.xial ribs, which extend to the suture posteriorly, but fuse 

 just before reaching tlie suture anteriorly; ribs on body-whorl fuse abruptly at angle; the intercostal 

 spaces appear as deep channels about as wide as the ribs; the suture appears very distinct, owing to 

 a sharp angulation on the upper part of the whorl, and a slight contraction at the base; body-whorl 

 rather short, rounded, smooth on base, except for fine, incremental lines; a])erture subquadrate, the 

 outer lip meeting the columella at almost right angles. 



Dimensions. — Long. 5.4 mm.; lat. 1.3 mm.; altitude of body-whorl, 1.7 mm. 



This species resembles T. siearnsu, but may he distinguished from that species 

 by more elevated, narrower and more numerous ribs and by the stronger angulalion 

 above. The specimen examined lacked prominent spiral sculpture as far as the 

 writer was sible to determine. This specimen was identified by Dr. Dall, imt the 

 species was omitted from tlie text prepared by Dall and JJartsch. 



Rather common in the upper San Pedro series of San Pedro and LosCerritos; 

 rare in the lower San Pedro series at Deadman Island and San INdro. 



Living.- — Gulf of California to Mazatlan (Carpenter). 



Pleistocene. — San Pedro (Arnold). 



285. Turbonilla (Strioturbonilla) similis C. H. Adams. 



Chemnitzia similis C. B. Ads., Catalogue Panama Shells, No. 228, Ann. N. Y. Lye. Nat. Hist., 

 Vol. V, 1852, p. 392. 



Shell small, slender, solid, milk-white, thick; nuclear whorls two and one-half, smooth, 

 helicoid, about one-third sunken, their axis being at right angles to the axis of the post- 

 nuclear whorls; post-nuclear whorls nine, somewhat flattened, ornamented by fourteen to eighteen 

 prominent, broad, convex, oblique, axial ribs, which traverse nearly the whole of the exposed 



