52 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 148 



Occurrence. — Type locality is U.S.N.M. 120, on Shields Ridge, 

 New Market quadrangle. Collected by the writer in the middle portion 

 of the lower limestone member of the Nolichucky (Crepicephalus zone) 

 at locality cnm/2. 



Types.— Uolotype : U.S.N.M. 62829. Plesiotype : U.S.N.M. 144581. 



Genus COOSIA Walcott, 1911 



Type species. — Coosia superba Walcott. 



COOSIA ALETHES (Walcott) 



Plate 6, figures 15-18; plate 7, figures 6-13 



Blountia alethes Walcott (part), 1916b, p. 397, pi. 64, figs. 1, la (only). 

 Coosia alethes (Walcott) Resser, 1938a, p. 71. 



Available material. — Abundant new specimens show that Walcott's 

 type cranidium is an immature individual of a species of Coosia that 

 attains large dimensions and is common everywhere in the upper 

 Crepicephalus zone of the Nolichucky. 



Description. — Glabella well defined by the axial furrow, unfurrowed, 

 not changing much in shape in cranidia from 2.3 to 18 mm, in length, 

 except for a gradual decrease of the convexity. Occipital furrow 

 straight, well impressed, occipital ring simple. Frontal area increasing 

 in length relative to the entire cranidium from 0.30 to 0.37 in the above- 

 mentioned size range. Border furrow becoming gradually wider and 

 shallower ; midlength of preglabellar field about equal to border width 

 (sag.) in small cranidia, decreasing to about half of border in adults. 

 Palpebral area decreasing in relative width with size ; palpebral lobes 

 regularly curved in early stages, becoming somewhat angular later. 

 Entire thorax preserved in an immature specimen that may represent 

 a holaspid and has 12 segments. The pygidium in this individual has a 

 long axis and the pleural lobes show 3 or 4 distinct pairs of furrows. 

 In larger pygidia the axis becomes shorter, equaling only half or less 

 of the pygidial length, and extends into a postaxial ridge. It is com- 

 posed of 3 rings and a terminal section distinct even on the outer 

 surface. The pleural lobes are slightly downsloping and furrowed in 

 a limited area near the axis, then flatten out into a wide, smooth, some- 

 what concave area that corresponds to the extent of the doublure. 

 The anterior marginal furrow is the only one that extends almost to 

 the lateral margin. The largest fairly complete cranidium is 18 mm. 

 long, but fragments indicate larger individuals. A large, incomplete 

 pygidium has a length of 22 mm. and a width of 44 mm. Surface of test 

 smooth except for wavy terrace lines on cranidial and pygidial borders. 



Discussion. — It may be questioned whether forms of Coosia de- 



