62 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



area separates the thickened, striated rim from the dorsal furrow. 

 Laterally the head is moderately and evenly convex, but longitudinally 

 the curvature is much greater. A shallow occipital furrow separates 

 a narrow ring. 



Sullivan formation ; (Iocs. 64c, b) Glacier Lake Canyon Vallcw 

 48 miles northwest of Lake Louise, Alberta. 



Holotypc. — U.S.N.M. No. 108776a; paratyp^s, Nos. 108776b, 

 108777a, b. 



ELLIPSOCEPHALOIDES Kobayashi, 1935 



Ellipsoccphaloidcs Kobavasiii, Journ. Fac. Sci. Imp. Univ. Tokyo, sect. 2, 

 vol. 4, pt. 2, p. 196, 1935. 



This generic name was assigned without proper study of the 

 specimens, for it perpetuates the false idea of relationship between 

 these trilobites and Ellipsocephalus. The species of Ellipsocepha- 

 loldes, moreover, are unique in several respects, and could not belong 

 to the lUaenuridae, which should have been apparent even before the 

 pygidium was known. Under present circumstances the best pro- 

 cedure is to place the genus in a new family, leaving the determination 

 of the family's position in trilobite classification to future study. 



Considerable variation in width of the anterior fixigene and the 

 more advanced course of the facial suture due to a more forward 

 position of the eye may be observed among the species here described. 

 Though these variations fall almost entirely on one side of the geno- 

 type, E. curtus (Whitfield), the narrow forms and those in which 

 the eye is farther back are not segregated as a separate genus since 

 sufficient gradation seems to exist to tie all together. EUipsocepha- 

 loidcs is apparently characteristic of Franconia horizons, for it is 

 associated with IdaJwia, Pscudagnostus, Briscoia, and other genera 

 of Franconia age. 



Species of Ellipsocephaloides vary considerably in shape. The 

 glabella is large and clearly defined, both by the dorsal furrow and 

 its elevation above the fixigenes. Some species have tliree pairs of 

 short glabellar furrows. Occipital furrow always developed, marking 

 off a neck ring, usually of even width throughout. Brim a simple 

 band, except in the wider species where a narrow rim is demarcated 

 by a shallow anterior furrow. The brim continues as the anterior 

 fixigene around the anterior angles and therefore curves much more 

 sharply in the narrow tlian in the wide forms. At their widest point 

 the fixigenes, exclusive of the eye band, vary from less than half to 

 more than the glabellar width at the same point. I'ixigenes between 

 the dorsal furrow and the eye are usually nearly fl;U, though they may 



