CRUSTACEA. 19 



In the Corniferous limestone at the Indian quarries, Onondaga county; East- 

 man's quarry, Waterville, Oneida county ; Howell's quarry, Lime Rock, Genesee 

 county. Variety pipa. In the Corniferous limestone everywhere; especially 

 abundant in the central and western outcrops al Waterville, Oneida eounty; 

 Phelps and Clifton Springs, Ontario county ; LeRoy and Lime Rock, Genesee 

 county; Clarence and Williamsville, Erie county, and in the boulders of decom- 

 posed chert in Ontario county; Falls of the Ohio. Also at Walpole and North 

 Cayuga, Province of Ontario. 



Phacops rana. 



PLATE VII, FIGS. 1-11 ; PLATE VIII, FIGS. 1-18; and PLATE VIII a, FIGS M-8S. 



Calymene bufo, var. rana, Greex. Monograph of the Trilobites of North America, p. 42. 1832. 



Calymene bufo, Hall. Geology N. ¥., Part, iv, p. 201. 1843. 



(ati/meite bufo, Owen. Geolog. Exploration of a pari of Iowa, Wis. and 111., p. 71. pi. xii. 6g. 1. IS-H. 



Phacops bufo, Emmons. Manual of Geology, p. 138, fig. 124 (6). 1860. 



Phacops rana, Hall. Descriptions New Species of Fossils, etc., p. 55. 1861. 



Phacops rana, Hall. Fifteenth Rept. N. Y. State Cab. Nat. Hist., p 93. 1862. 



Phacops rana. Meek and Wokthen. Geol. Surv. 111., vol. iii., p. -'.47, pi- xi, tigs, la-e. 1868. 



Phacops rana, Nicholson. Palaont. Province of Ontario, p. 123. figs. 5, 6a. 1873. 



Phacops rana, Hall. Illustrations of Devonian Fossils, pi. vii, figs. 1-11 ; yiii. tigs. 1-17. 1S7C 



Phacojis rana, Whttfield. Geology of Wisconsin, vol. iv. p. 339, pi. xxyi. Hl.'-s 17-1'.'. 1882. 



Compare Phacops rana, Walcott. Palseont. Eureka Districl : Monog U.S. Geol. Suvv., vol. viii. p. 207. 1SS4. 



General Form and Proportions. Outline elongate sub-oval ; greatest width 

 (measured at the posterior margin of the cephalon) to axial length as I to 2. 

 The cephalon, thorax and pygidium are to one another in length as 1.5 to 2 

 to 1. Thoracic margins straight, sub-parallel, gently converging posteriorly, 

 connecting the curves of the cephalon and pygidium, which are approxi- 

 mately arcs of large and small circles respectively, the former with its center 

 upon the occipital ring, the latter central upon the eighth thoracic segment. 



Cephalon arcuate, sub-semicircular, the regularity of the outline interrupted 

 by the slight protrusion of the glabella and the genal extremities. Frontal 

 margin obscure, concealed by the overhanging glabella ; lateral edges faintly 

 marginate and rounding to the obtuse genal angles: occipital margin nearly 

 straight, bending backward on the axis. Occipital annulation strong, and 

 equal in size to the segments of the thorax; occipital furrow narrow and 

 becoming obsolete upon the cheeks. 



