NO. 3 CAMBRIAN TRILOBITES l6l 



The memoir on the Cambrian Faunas of China* also contains 

 many descriptions and illustrations of trilobites. 



One of the marked features of the present paper is the description 

 of several genera of the order Proparia: Menomonia, Millardia, 

 Dreshachia, and Norwoodia. These taken in connection with the 

 genus Burlingia^' of the Middle Cambrian, establish the existence 

 of a strong group of the order in Cambrian time. 



CHANGE IN STRATIGRAPHIC POSITION OF THE 

 WEEKS FORMATION" 



On account of the presence of Crepicephalus texantis Shumard in 

 the Weeks formation, the strata forming it were referred to the 

 Middle Cambrian. My recent studies of C. texanus and its strati- 

 graphic and geographic range have led me to the conclusion that it 

 is an Upper Cambrian species and that the formations containing it 

 should be referred to the Upper Cambrian. This question will be 

 considered in detail in a subsequent paper on the Upper Cambrian 

 formations. 



DESCRIPTIONS OF GENERA AND SPECIES 



Order PROPARIA Beecher 



Family Menomonid^, new family 



Proparia of primitive aspect, with large free cheeks; eyes small. 

 Thorax with 23 to 42 segments ; pygidium small. 



The genera referred to this family are Menomonia, Millardia, and 

 Dreshachia. 



MENOMONIA, new genus 



General form efongate, lance-shaped, with cephalon at the broad 

 end ; strongly convex ; axial and pleural lobes strongly outlined. 



Cephalon transversely semicircular with rounded genal angles 

 on the postero-lateral limbs ; marginal border broad and convex on 

 the cranidium, flattening out on the free cheeks ; posterior margin 

 strongly defined by a deep furrow that merges into the intramarginal 

 furrow of the free cheek.- Glabella truncato-conical, about one-half 

 the length of the cranidium, and marked by three pairs of short 

 lateral furrows ; occipital ring of medium width and well defined by 



^ Research in China, Carnegie Inst, of Washington, 1913, Vol. 3, Pub. No. 

 54, pp. 1-276, pis. 1-24. 



^ Cambrian Trilobites, Smithsonian Misc. Coll., Vol. 53, No. 2, 1908, p. 14. 



^ Nomenclature of some Cambrian Cordilleran Formations, Smithsonian 

 Misc. Coll., Vol. 53, No. I, 1908, p. 10. 



