NO. 3 CAMBRIAN AND OZARKIAN TRILOBITES IO5 



MALADIA AMERICANA Walcott 



Plate 16, figs. 23-26 



Maladia americana Walcott, 1924, Smithsonian Misc. Coll., Vol. 75, No. 2, 

 p. 59, pi. 12, fig. 2. 



The illustrations present practically all that is known of this species. 



Formation and locality. — Upper Cambrian: (54x) Ovid forma- 

 tion. Sixty feet (18.3 m.) from top of bed 4, north side of Two Mile 

 Canyon near its mouth, two miles (3.2 km.) southeast of Malad, 

 Idaho. 



Genus MODOCIA Walcott 



Modocia Walcott, 1924, Smithsonian Misc. Coll., Vol. 75, No. 2, p. 59. 



The genus Modocia is based on the cranidia of a species known for 

 more than 60 years that has been referred to six different genera by 

 authors. It does not fall strictly within any described genus and to 

 avoid further confusion a new name is proposed for it. 



The cranidium of Modocia is characterized by its strong, sub- 

 conical glabella without definite glabellar furrows ; occipital furrow 

 clearly defined -and extending across the fixed cheeks within their 

 posterior margin; occipital segment rather narrow: fixed cheeks 

 broad and merging into strong postero-lateral limbs and the frontal 

 limb which is of medium width : frontal border rounded, narrow at 

 the ends and broadening very gradually to the center owing to the 

 course of the facial outline which cuts the border on a line with the 

 eyes and then curves sharply and continues obliquely across the 

 border nearly to the center and possibly the two branches meet at 

 the center, but the material in hand does not prove this : palpebral 

 lobes small and located just back of the line of the longitudinal center 

 of the cranidium. The fixed cheeks must have been of medium size. 

 An associated pygidium was illustrated by Walcott.' 



Genotype. — Arionellus {Crcpiccphalus) oweni Meek and Hayden. 



Range. — Upper Cambrian : Black Hills, South Dakota. Big Horn 

 Mountains, Wyoming, and probably in the Cordilleran area of 

 western North America. 



Observations. — The cranidium of Modocia suggests that of species 

 which have been referred to Crepicephalus, Blountia, Bathyuriscus, 

 Asaphiscus, etc. The cranidium, however, differs in the direction of 

 the facial sutures through the frontal border and the very broad fixed 

 cheeks. 



' Monogr. U. S. Geol. Surv., 1884, Vol. 8, pi. 10, fig. 3a. 



