26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 95 



PLETHOPELTIS Raymond, 1913 



Plethopeltis levis (Walcott) 



Arioncllus Icvis Walcott, U. S. Geol. Surv. Mon. 32, p. 462, pi. 65, fig. i, 1899. 



Upper Cambrian; Crowfoot Ridge, northwestern Yellowstone Na- 

 tional Park, Wyoming. 



Holotype.—U.S.'HM. no. 35230. 



POULSENIA, n. gen. 



Associated with Ingle fieldia in Greenland and elsewhere in the Ap- 

 palachians are many species of a closely related trilobite. Poulsen set 

 these species ofif by assigning them to Solenopleura, whereas Walcott 

 placed the more southerly forms in Ptychoparia. 



Diagnosis. — Small trilobites of average form. Cranidium rather 

 wide, convex in both directions ; facial sutures diverging slightly an- 

 terior to the eyes, but owing to the infolding of the anterior angles 

 appear to converge. Glabella well defined, tapering, truncated or 

 rounded in front ; two thirds or more of the length of the cranidium. 

 Glabellar furrows two or three short pairs ; neck furrow and ring well 

 defined. Eyes small, situated in middle or somewhat back of the middle 

 of the head. Eye lines present, brim consisting of a more or less 

 thickened rim and a preglabellar area of varying relative width. 



Judging from somewhat uncertain material, the thorax consists of 

 about 15 segments. Pygidium small, well fused, with axis well de- 

 fined, and with pleural grooves. 



Genotype. — Solenopleura grbnzvalli Poulsen. 



Range. — Upper Lower Cambrian of North America. 



Comparisons. — Superficially Poulsenia resembles the Atlantic Prov- 

 ince Middle Cambrian genus Solenopleura, but it is doubtful if this 

 resemblance involves any relationship. On the other hand, Poulsenia 

 appears simply to be the convex forms of the Inglefieldia stock. 



Poulsenia gronwalli (Poulsen) 



Solenopleura groint'olli Poulsen, Meddels. Gr^nland, vol. 70, p. 265, pi. 15, 

 fig. 28, 1927. 



Lower Cambrian, Cape Kent ; Cape Kent, northwest Greenland. 

 Holotypc. — Min. Mus. Copenhagen ; cast, U.S.N.M. no. 70980. 



Poulsenia similis (Poulsen) 



Solenopleura similis Poulsen, Meddels. Grjzinland, vol. 70, p. 265, pi. 15, 

 fig. 26, 1927. 



Occurrence same as preceding. 



Holotype. — Min. Mus. Copenhagen ; cast, U.S.N.M. no. 70981. 



