274 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



Fixed cheeks comparatively broad ; frontal limb about one-fifth 

 the length of the head, curving gently from the dorsal furrow to the 

 anterior margin ; posterior limb elongate, with a strong furrow from 

 the dorsal furrow to its extremity. Palpebral lobe elongate, separated 

 from the fixed cheeks by a groove within the margin ; surface covered 

 with fine lamellose strise. 



This species is much larger than Lonchoccphalus calciferus. The 

 largest cranidium in the collection has a length of 30 mm., and a 

 large pygidium has a length of 37 mm. with a width of 60 mm. 



The surface is finely punctate and marked by very fine, irregular 

 imbricating lines. 



Observations. — This species differs from Dicellocephalus minne- 

 sotcnsis in details, but it appears to come within the limits of the 

 genus. 



In the larger specimens the frontal rim is broad and slightly 

 convex and in some specimens merged directly into the frontal limb. 

 In the small specimens the frontal rim is more rounded and a distinct 

 broad groove separates it from the narrow frontal limb. Comparing 

 specimens of the cranidium 8 to 10 mm. in length with specimens 

 30 mm. in length two species would appear to be indicated, but there 

 is a gradual transition by the widening out and flattening of the 

 frontal limb so that the two extremes are united by forms that grade 

 from the narrow rounded frontal limb to the broad flattened rim. 



A somewhat similar gradation exists between small pygidia and 

 large pygidia. In the small pygidia the median lobe extends back 

 nearly to the posterior margin. The space between the margin and 

 the end of the lobe increases in size until in the large forms, 37 milli- 

 meters in length, the flattened border is nearly one-third the length 

 of the pygidium. 



Formation and locality. — Upper Cambrian, Hoyt limestone: (76) 

 Arenaceous limestone at Hoyts quarry, 4 miles (6.4 km.) west of 

 Saratoga Springs; and (76a) in a railroad quarry, i mile (1.6 km.) 

 north of Saratoga Springs ; both in Saratoga County, New York. 



DICELLOCEPHALUS TRIBULIS, new species 



Plate 44, figs. 8 and 8a. 



A second well-marked species of Dicclloccphalns occurs in associa- 

 tion with D. Iiartti. It is closely allied to D. misa Hall of the " St. 

 Croix sandstone " of Wisconsin. It differs in having slightly wider 

 fixed cheeks, a more rounded frontal rim, and granulated surface. 



The pygidium provisionally referred to this species also varies 

 considerably from the pygidium referred to D. misa. 



