372 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 5/ 



DIKELOCEPHALUS TEXANUS, new species 

 Plate 65, fig. 4 



Of this species only the fragment of the posterior half of the crani- 

 dium illustrated has been seen. This indicates a large form compar- 

 able with Dikelocephalus minnesotensis. It differs from that in hav- 

 ing the palpebral lobe farther forward, and from D. vanhornei in 

 having the palpebral lobe nearer the glabella. With better specimens 

 probably other differences might be found. 



The outer test has been exfoliated, but from the impression of the 

 inner surface it is evident that it was marked by rather strong, nar- 

 row, irregular lines. 



Formation and locality. — Upper Cambrian: (70a) Wilberns for- 

 mation, Baldy Mountain, near Morgans Creek, 8 miles (12.8 km.) 

 northwest of Burnet, Burnet County, Texas (C. D. Walcott, 1884). 



Fragments of a large trilobite that may be a species of Dikeloceph- 

 alus occur in the lower portion of the Arbuckle limestone of Okla- 

 homa (i2g), 150 miles (240 km.) north of the locality (70a) where 

 D. texanus occurs. Unfortunately there is not sufficient material by 

 which to compare the cranidia. The fragments at both localities indi- 

 cate a large species comparable with D. minnesotensis. 



DIKELOCEPHALUS ? TRIBULIS Walcott 



Plate 63, figs. 8-10. loa 



Dicellocephalus tribulis Walcott, IQ12, Smithsonian Miscellaneous Coll., 

 Vol. 57, No. 9, p. 274, pi. 44, figs. 8, 8a. (Illustrates and comments on 

 species.) 



With only imperfect specimens of the cranidium and a fragment of 

 a pygidium doubtfully referred to the species, it is difficult to make a 

 satisfactory generic reference. The position of the palpebral lobes 

 and the slightly concave frontal limb suggest Conokephalina misa 

 (Hall) (pi. 68, figs, i, 2), while the form of the glabella is much like 

 that of Dikelocephalus hartti. It may be that with the discovery of 

 entire specimens of this species and Conokephalina misa the two 

 will be found to be congeneric and an intermediate form between 

 Dikelocephalus and Saukia. 



The largest specimen of the cranidium in the collection has a length 

 of 16 mm. 



Formation and locality. — Upper Cambrian: (76) Hoyt formation; 

 arenaceous limestone at Hoyts quarry, 4 miles (6.4 km.) west of Sara- 

 toga Springs, Saratoga County, New York (C. D. Walcott and 

 Cooper Curtice, 1883). 



