94 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



Thorax contains 10 segments in all species of which entire speci- 

 mens are known, all with a narrow median pleural furrow and ending 

 abruptly in a blunt spine. 



Pygidium consists of two parts, the posterior one being a welded 

 shield somewhat like the tail of Asaphiscus and the anterior one a 

 pleura-like segment extending into long spines, but attached firmly 

 to the more solid shield. In some species two or more rings are 

 visible on the axis and several lateral furrows at the front edge of 

 this shield. Border or pygidium quite broad in some species. Appar- 

 ently a doublure as wide as the border, occurs under it. 



Derivation of name. — House Range, Utah. 



Genotype. — Dolichomctopus (Housia) varro Walcott. 



Range. — Upper Cambrian, Cordilleran area of Canada and the 

 United States. 



Observations. — Housia differs from Ccratopyge forficula Sars, the 

 type of the latter genus, in many important respects. In Ceratopyge 

 the glabella is distinctly separated by a strong dorsal furrow, passing 

 all the way around. There is also no wide frontal border and rim. 

 There is a very narrow rim, almost wire-like, in which the suture 

 could not have been intramarginal in the same manner as in Housia. 

 The suture also diverges a little more in Ceratopyge. The glabellar 

 furrows are definite, extending straight across and not oblique to 

 the glabella. 



The pygidia of the two genera are quite dift'erent. That of Ccra- 

 topyge is completely fused. There is no wide rim but simply a wire- 

 like one. Axis relatively high and annulated. The two lateral spines 

 of the Ceratopyge tail are not the definite segments as in Housia, but 

 arise from the second or third segment and are fused with the rim. 



In addition to the two described species of Housia there are two 

 from the Goodsir formation that will be published in a future paper. 



HOUSIA CANADENSIS (Walcott) 



Plate 22, figs. 10, II 



Ccratopyge canadensis Walcott, 1912, Smithsonian Misc. Coll., Vol. 57, No. 7, 

 p. 233, pi. 35, figs. 17, 20, 21 (not figs. 13-16, 18, 19, 22). 



Observations. — The figures of Housia canadensis published in 

 191 2 are all of more or less distorted specimens which have now been 

 referred to three species. Entire individuals are available for most 

 of the species and so the reference of the various cheeks and pygidia 

 to the cranidia is much more certain than where entire specimens 

 are lacking. 



