362 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



DOLICHOMETOPUS BATON, new species 

 Plate 51, figs. 2, 2a-b 



This species is preserved in a fine, dark argillaceous shale. The 

 largest dorsal shield has a length of nearly 60 mm. As far as can be 

 determined, the surface of the test was finely punctate. Seven 

 thoracic segments of the usual form except that the extremities nar- 

 row more rapidly to a sharp, shghtly backward curving point. 



Dolichometopus baton differs from D. sueciciis, D. prodnctus, D. 

 hoccar and D. bion by its smaller palpebral lobe and termination of 

 the pleural lobes of the thoracic segments. From D. f bessus is differs 

 in position and relative size of palpebral lobes and more transverse 

 pygidium. The thoracic segments are quite similar in- both species. 



Formation and locality. — Middle Cambrian : (3J) Wolsey ? shale ; 

 above the quartzitic sandstones in a shale corresponding in position 

 to the upper part of shale No. 6 of the Dearborn River section,^ about 

 6 miles (9.6 km.) west-northwest of Scapegoat Mountain on the Con- 

 tinental Divide between Bar Creek and the headwaters of the south 

 fork of the North Fork of Sun River, Coopers Lake quadrangle 

 (U. S. G. S.), Powell County, Montana. 



DOLICHOMETOPUS ? BESSUS, new species 

 Plate 51, figs. 3, sa-c 



Fragments of this species contained in a fine, buff-colored, argil- 

 laceous shale indicate that the dorsal shield attained a length of 30 

 mm. A smaller entire specimen has a length of 22 mm. The outer 

 surface of the test appears to have been punctate and the seven 

 thoracic segments terminate in sharp, gently curved points very simi- 

 lar to those of D. baton (pi. 51, fig. 2). 



Dolichometopus f bessus differs from its most nearly related 

 species, D. baton, by its smaller palpebral lobe and its more elongate 

 pygidium which is also more abruptly curved backward at the antero- 

 lateral margin. 



This species has many of the characters of Bathyuriscus bantius 

 (pi. 49, figs. 2, 2a), and brings the genera Dolichometopus and Bathy- 

 uriscus very close to each other. 



Formation and locality. — Middle Cambrian: (62!) Wolsey shale 

 interbedded in upper part of Flathead sandstone, Sixteen Mile Can- 



* Smithsonian Misc. Coll., Vol. 53, No. 5, 1908, Walcott, Cambrian sections of 

 the Cordilleran area, p. 202. 



