Weller — KinderJiook Faunal Studies. 119 



fauna, although not sufficiently well preserved specimens have 

 yet been found to admit of determining their distinguishing 

 characters. 



CEPHALOPODA. 

 Orthoceras whitei Win. 



PL IX. f. 4-5. 



Shell annulated, gradually tapering at an angle of about 5°; 

 subelliptical in cross-section ; septa deeply concave, situated 

 at distances of about 4-5 mm. At the largest end of the 

 largest type specimen, the louger diameter of the cross-sec- 

 tion is 32 mm., and the shorter 25 mm. The annulations 

 are sharply angular or rounded, separated by regularly con- 

 cave furrows; ten of them occupy a space of 63 mm. In 

 the smaller specimens referred to this species, the annulations 

 and septa are much closer together, and sometimes the annu- 

 lations have a broad, shallow, retral sinuosity. Siphuncle 

 rather large, situated excentrically along the longer diameter. 

 Surface of the casts marked by fine encircling striae which 

 are parallel with the annulations, in some specimens being 

 obsolete. 



Remarks. This species is not uncommon iu the Chonopectus 

 fauna, though it exhibits a considerable range of variation in 

 size. The two specimens illustrated are both included among 

 those labeled as type specimens in the University of Michigan 

 collection. The larger one probably represents about the 

 maximum size of the species. The species belongs to the 

 annulate division of the genus which is represented by several 

 species in the Devonian faunas in America, but which is 

 uncommon in the Carboniferous. 



Orthoceras heterocinctum Win. 



PL IX. f. 6. 



This is an annulated species closely allied to O. whitei, and 

 is possibly no more than a variety of that species. None of 

 the type specimens are as large as the largest O. lohitei, and 

 the annulations are much more unequal, in some specimens 

 being nearly obsolete and in others being nearly 



