NO. 13 DIKELOCEPHALUS AND OTHER GENERA 375 



thoracic segments of the two genera are similar. The pygidium of 

 Saukia is less expanded and more elongate than that of D ik ch- 

 eep halus. 



Saiikia differs from Osceolia (pi. 68, figs. 4-10) in having a concave 

 instead of a depressed convex anterior margin to the cephalon, and 

 a rounded, smooth margined pygidium. 



It differs from CalvineUa (pi. 69, figs. 1-5) in form of glabella, 

 absence of a strong occipital spine, and proportionately less trans- 

 verse pygidium. These characters may possibly be accompanied by 

 other differences in the thorax not at present known. 



The species now referred to the genus are : 



Saukia coloradocnsis Walcott (text figs. 13-16, p. 376) 

 Saukia crassimarginata (Whitfield) (pis. 61, 65, 66) 

 Saukia falla.v Walcott (pi. 67, figs. 21, 21a, 22, 22a) 

 Saukia junia Walcott (text fig. 17, p. 378) 

 Saukia ?? Icptcrnarum (Wiman) 

 Saukia leucosia Walcott (pi. 67, figs. 14-17) 

 Saukia lodcnsis (Whitfield) (pi. 65, figs. 1-3) 

 Saukia marica (Walcott) (pi. 64, figs. 6, 6fl) 

 Saukia pepinensis (Owen) (pi. 67, figs. 1-13) 

 Saukia pyrene Walcott (pi. 6y, figs. 18-20) 

 Saukia rustica Walcott (text figs. 18, 19, p. 383) 

 Saukia stosei Walcott (pi. 69, figs. 3-5) 

 Saukia zvardi Walcott (pi. 69, figs. 1-2) 



Stratigraphic range. — Found in both the upper and lower zones of 

 the St. Lawrence formation and Lower Ozarkian. 



Geographic distribution. — Several of the species are found in the 

 upper Mississippi valley in Wisconsin and eastern Minnesota. Saukia 

 pepinensis occurs in central eastern Nevada and 6*. falla.v is from 

 central Texas. Saukia eoloradoensis occurs at Quandary Peak, 

 Summit Coutity, Colorado. Two species, S. stosei and S. wardi, are 

 from the Appalachian Province in southwestern Pennsylvania and 

 western Virginia. 



Observations. — The species referred to Saukia fall into two groups. 

 The first, characterized by 6". lodeusis, S. eoloradoensis, and .S". crassi- 

 marginata, which most nearly approach Dikeloccphalus, except in 

 the character of the frontal limb and margin. The second, character- 

 ized by 6^. pepinensis and its allies, 6*. leucosia, S. pyrene, S. stosei and 

 5. zvardi, which appear to be intermediate between Dikeloccphalus 

 and forms referred to Anomocare, but with a leaning towards Dikelo- 

 ccphalus. With the discovery of entire specimens of the several 

 species it may be that a rearrangement of the generic references of 

 the several species now placed under Saukia will be necessary. 

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