RAYMOND: NEW AND OLD SILURIAN TRILOBITES. 35 



pies less than half the length, and the furrows are long, curve back- 

 ward, the last pair meeting, as usual, and the inner ends of the other 

 pairs being very close together. The free cheeks are small, the eyes 

 opposite the ends of the second pair of glabellar furrows and near the 

 dorsal furrows. The fixed cheeks are wide, with coarse pits, and the 

 genal spines are short and slender. The glabella seems to be devoid 

 of granulation. 



Of the thorax, only five segments have been seen. It seems to be 

 in all respects like that of Ch. niagarensis. No pygidium can defi- 

 nitely be assigned to this species. All the specimens found at Wauwa- 

 tosa seem to agree with the pygidium from Rochester which has been 

 assigned to Ch. niagarensis. Weller has, however, figured a cheirurid 

 pygidium found near Chicago, in which the central spines of the 

 pygidium are shorter than the others. This pygidium is in this respect 

 unlike the one here assigned to Ch. niagarensis and may belong to Ch. 

 welleri. In cephalon and thorax, Ch. welleri is closely allied to Ch. 

 quenstedti Barrande, of Bohemia. This species has the inner spines 

 so short that the pygidium appears to possess only two pairs of spines. 

 It may be that Ch. welleri has a pygidium intermediate in form be- 

 tween Ch. insignis or Ch. niagarensis, and Ch. quenstedti. 



Measurements: — A large cranidium, one of the cotypes (M. C. Z. 

 14) is 33 mm. long and 62 mm. wide; the glabella is 19 mm. wide at 

 the neck-ring and 25 mm. wide at the frontal lobe; the frontal lobe 

 is 15 mm. long. This has about the same length as Ch. dilatatus, but 

 the disparity of the other dimensions should be noted. The figures 

 for Ch. welleri are always given first. Length, 33, 35, width, 62, 52; 

 width glabella at neck, 19, 20, at frontal lobe, 25, 31. The longer 

 specimen is the narrower, and has a wider glabella, thus showing a 

 great reduction of the cheeks. The cranidium of a smaller cotype 

 (M. C. Z. 630) is 14.5 mm. long, 25 mm. wide, the glabella is 7 mm. 

 wide at the neck-ring, 11 mm. wide at the frontal lobe, and the frontal 

 lobe is 7 mm. long. Large specimens of this species seem to have 

 been abundant, and the largest glabella in the collection is 45 mm. long, 

 and, so far as I know, the largest American cheirurid. Restored with 

 the proportions of Ch. insignis, this trilobite would have a length of 

 145 mm. or nearly 6 inches. The Bohemian Eccoptochile claviger 

 (Beyrich) equals this size. 



Formation and locality: — The types are from the Niagaran at 

 Wauwatosa, Wise. The species occurs also in the Clinton of New 

 York, the Waldron of Indiana, Silurian of Tennessee, and Guelph of 

 Ontario. It is probably the most cosmopolitan species of Cheirurus. 



