<>norr 



HALO POD A 



799 



imliration- of ;i linear or t hicki-iie-l oval scar extending from the inner margin of 

 the -iplional lu'inls aloni: tin- major diameter of the septum to near the inner 



lor-al margin. 



KIK- 1" V. rlii-al median section of O. minntnottnix showing the form of tin- siphonal l-ad-. . I.'. 



The external surface is covered with numerous low longitudinal ribs, thirty- 

 tive or forty in mi in her on the later portions of the shell. Among a number of 



-I imens representing this species there are none of the body chamber. The 



septate portions afford no satisfactory indication of the expansion which charac- 

 terizes the genus Oncoceras; still the material presents many similarities to the 

 -peries ],'-.Til>"l l'\ \Vliit.M\e-' a- OyrtOOtTtU <//"//.,'..//-.. from tin- I. o\\er Silurian 

 at many localities in Manitoba. The latter possesses a somewhat similar curvature 

 of the septa, though a deeper concavity and a greater obliquity ; and it also has a 

 similar external ornamentation. Whiteaves' figures indicate a species with very 

 -liirht arruation and a decided expansion of the tube toward the aperture, and 

 nearly the entire extent of the swelling is septate, the hotly-chamber occupying but 

 a small part of it. It would seem wiser for the present to refer such shells to 

 ihi,;,,;-ri<s as they must be regarded as differing notably from typical forms of 

 <'y rim-eras. The Minnesota specimens are hence thus referred, though they all 

 lack the body-chamber. 



Cation and locality.- In tin- Galena limestone at Hader, StewarUvllle, Mantorvllle, Pleasant 



and Lime City, Minn. A -.iriK-U- fnitfin.'nt .f the apical |.rtinn of a shell having the aspect of itu- 

 I. lit with th<- septa cloaer Untether Is from tti- llmNon Illver hori/on at Cran^.-r. Minn. 

 iluMum Keffiiter. No*. 258, 4106, 82M, 8206, 8296. 



ONCOCKKAS LYCUS, //'///. 1S61. 



1'I.ATK I.VIII. HiiS. I-* 

 Orthorenu lyfum OALI. Kept. Supt. (te.il. Siirv. Wisconsin, p. 45. 



Shell arcuate, with an arc of short radius on the ventral curve and a 



Trn. K-.yl Boo. Cnl, TO|. Til, wet. IT. p. ML pt. (III. t* X I; pi. XT. t. 4. UM. 



