NO. 3 UPPER CAMBRIAN TRILOBITE FAUNAS — RASETTI 109 



Occurrence. — Red beds at the base of the NoHchucky (Cedaria 

 zone) E. of Rogersville (locality cnd/1). 



Types. — Holotype (pygidium) : U.S.N.M. 144717. Paratypes: 

 144718. 



MODOCIA CRASSIMARGINATA Rasetti, new species 



Plate 2, figures 1-9 



Available material. — Numerous cranidia and pygidia well preserved 

 in limestone. 



Description. — Glabella rather plump, defined by a deep axial furrow, 

 rounded in front, unfurrowed; occipital furrow well impressed, occi- 

 pital ring simple. Preglabellar field downsloping, short (sag.), on the 

 average shorter than the border width (sag.), although there is vari- 

 ability in this character. Border convex, wide (sag.). Ocular ridges 

 faintly indicated ; palpebral lobes narrow, defined by a shallow palpe- 

 bral furrow, about 0.3 times the glabellar length, somewhat in advance 

 of level of glabellar midpoint. Palpebral area convex, on average down- 

 sloping, 0.4 times the glabellar width. Anterior sections of facial suture 

 somewhat divergent, curving inward after crossing the border furrow, 

 rounding off the anterior cranidial angles. Posterior section first di- 

 rected outward, curving backward, rounding off the extremity of the 

 posterior area which is deeply furrowed. 



Pygidium with a stout, barely tapered, well-rounded axis showing 

 3 rings and a terminal section, not reaching the margin. Pleural re- 

 gions transversely downsloping and convex longitudinally, showing 3 

 pairs of well-impressed furrows and 2 pairs of slightly shallower inter- 

 pleural grooves, all fading out toward the margin without the presence 

 of any defined border furrow or border. 



Surface of test with inconspicuous ornamentation. Some of the 

 cranidia show a punctate surface, the puncta being small and so dense 

 as to produce the effect of a fine granulation ; other cranidia appear al- 

 most smooth. Pygidia where the test is preserved show a very fine 

 granulation. 



Length of the largest cranidia 17mm. Length of largest pygidium 

 6.5 mm., width 14 mm. 



Discussion. — Species of this type were assigned to Syspacheilus (see 

 discussion of Modocia) ; for example, the present form does not seem 

 to differ greatly from Syspacheilus camurus Lochman (1940), S. 

 dunoirensis (Miller), as figured by Lochman and Hu (1961), and 5. 

 praecedens Lochman and Hu (1961). From the latter two forms, 

 where the pygidium is known, the present species differs in the more 

 deeply furrowed pleural lobes. Armonia pelops Walcott is also close to 



