FOSSILS OF THE DEVONIAN. 



209 



Pygidium moderately convex, sub trigonal in outline; length two- thirds 

 of the width; ancerior lateral angles a little rounded, lateral margins con- 

 verge with a slight outward curve to the base of a strong upward-curving 

 spine that forms the posterior extremity of the pygidum, the spine curving 

 up at an angle of 45 in adult specimens and from 35 to 25 in the younger 

 individuals; median lobe less convex than the lateral lobes and two-thirds 

 as wide, uniformly rounded, and tapering gradually to the posterior extrem- 

 ity; marked by 13 to 15 well-defined annulations and an elongate terminal 

 ring; lateral lobes with 10 to 11 strongly defined ribs that curve in their 

 outer half obliquely backward, terminating just within the narrow margin. 



Surface of the glabella, thoracic segments, and pygidium punctate. 



This is the largest trilobite } 7 et discovered in the Devonian of the West. 

 Individuals 35 cm in length are indicated by the larger fragments, and one 

 hypostoma is 7 cm in length. 



The pygidium resembles that of Dalmanites micrurus of the Lower 

 Helderberg- limestone of New York (Pal. N. Y., vol.iii, p. 359, plate Ixxiv, figs. 

 13-20), but differs in the less number of annulations in the lobe and in the 

 punctate surface. To D. anchiops Green (sp.) (Pal. N. Y., Illustrations of 

 Devonian Fossils, Crustacea, pi. ix) of the Upper Helderberg limestone of 

 New York, it has a strong resemblance when compared to young individ- 

 uals, but differences exist that readily separate the species. 



The late Mr. F. B. Meek described and illustrated fragments of an 

 unknown form of Dalmanites, from the Devonian limestone of the Pinon 

 Eange of Central Nevada, and the two pygidise illustrated are closely related 

 to those from the Eureka District, the character of the surface, which is 

 smooth or granulose, as seen in badly weathered specimens, alone appear- 

 ing to be different. 



The specific name is given as a slight recognition of Mr. Meek's ex- 

 tended and valuable contributions to our knowledge of the invertebrate 

 Paleontology of the Western United States. 



Formation and locality. Lower horizon of the Devonian limestone, 

 Comb's Peak, and on the divide at the head of the Reese and Berry Cafion, 

 Eureka District, Nevada. 

 14 c D w 



