58 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



IDAHOIA new genus 



PI. 14 fig. I. (Nat. size.) Outline drawing of the tj'pe cephalon and 



associated pygidium. 



Idahoia is characterized by the broad frontal Hmb, which is com- 

 posed of a border, a wide rim and the rim of the free cheeks. Suture 

 entirely intramarginal. Occipital furrow absent. Pygidium concave 

 on the pleural portions. 



Genotype. — /. serapio new species. 



Range. — Upper Cambrian. Idaho. 



IDDINGSIA new genus 



PI. 12, fig. 6. (Nat. size.) Outline of the cranidium. 

 Iddingsia is represented by the cranidium only, although other 

 parts may be present in the extensive collections. 



Genotype. — Ptychoporia similis Walcott (Mon. U. S. Geol. Surv., 

 8, 1884, p. 52, pi. 10, fig. 10). 



Range.- — Upper Cambrian. Eureka District. 

 « 



IRVINGELLA Ulrich and Resser MSS new genus 



PI. 10, fig. 3. (Large specimen.) Diagrammatic drawing of the type 



cranidium. 



Jrvingelia is characterized by its very large eyes, narrow fixed 

 cheeks and exceedingly narrow free cheeks. It is a very large genus. 



Genotype.- — /. major Ulrich and Resser MSS. 



Range. — Upper Cambrian and Ozarkian. Appalachians, Missis- 

 sippi Valley, Rocky Mountains and Nova Zemlya. 



ISOTELOIDES Raymond 



PI. 13, fig. 6. (Nat. size.) Outline drawing of the genotype, /. whitfieldi 



Raymond. 



The genus Isoteloides is represented in many of the Upper Ozarkian 

 and Canadian collections of the Rocky ]Mountains. 



KINGSTONIA new genus 

 PI. 14, fig. 2. (X4-) Outline drawing of the genotype. 



Kingstonia is a small trilobite characterized by the practical ab- 

 sence of the dorsal furrow. Many undescribed species belonging to 

 this genus are in our collections. It resembles in certain features 

 Illaenurus Hall (pi. 14, fig. 7), Symphysurina Ulrich (Smithsonian 

 Misc. Coll., Vol. 75, No. I, 1924, p. 37) and Tsinania (pi. 14, fig. 6). 



Genotype. — Kingstonia apion new genus. 



Range. — Upper Cambrian, Appalachians, Missouri, Oklahoma. 

 Cordillera of Canada and United States. 



