356 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



Dolichometopus Koken, 1896, Die Leitfossilien, Leipzig, p. 15. (Briefly de- 

 scribed under family Paradoxididse.) 



Dolichometopus Frech, 1897, Leth. geog., Pt. i, Leth. Pal., Vol. 2, p. 65. 

 (Relates the genus Niobc to Dolichometopus, and identifies the latter 

 with Bathyuriscus Walcott.) 



Dolichometopus Matthew, 1897, Trans. Royal See. Canada, 2d ser.. Vol. 

 3, Sec. 4, p. 184. (Discusses the genus and illustrates Angelin's type.) 



Dolichometopus Matthew, 1897, Idem, p. 195. (Suggests that Billings's 

 Bathyuriscus, extended by Walcott, is a subgenus of Dolichometopus.) 



Amphoton Lorenz, 1906, Zeits. deuts. geol. Gesells., Vol. 58, Pt. 2, p. 75. 

 (Described as a new genus.) 



Dolichometopus Lorenz, 1906, Idem, p. 74, text figure. (Compares Dolicho- 

 metopus and Bathyuriscus.) 



Dolichometopus Walcott, 1913, Research in China, Vol. 3, Carnegie Inst, of 

 Washington, Pub. No. 54, p. 215. (Briefly discusses genus and refers 

 Lorenz's Amphoton to Dolichometopus.) 



General form elongate oval, distinctly trilobed and rather convex. 

 Cephalon semicircular with postero-lateral angles prolonged in sharp 

 spines ; cranidium large, with strong fixed cheeks, long postero- 

 lateral limbs and inconspicuous antero-lateral limbs ; glabella more or 

 less broadened anteriorly and slightly contracted midway ; very faint 

 traces of three pairs of short glabellar furrows are to be seen on 

 cast of the interior of the test of specimens of the type species' 

 and more definite furrows on D. productus; frontal limb narrow, 

 slightly rounded or flattened and with a furrow of varying size and 

 depth between it and the glabella ; occipital ring broad and defined 

 from the glabella by a shallow, gently concave furrow ; none of the 

 species appear to have an occipital spine although it might be expected 

 on D. tontoensis; palpebral lobes elongate and varying in the various 

 species from one-fifth (D. tontoensis) to three-fifths of the length 

 of the cranidium {D. productus) ; free cheeks of medium size and 

 terminating in a strong spine at the genal angle. The facial sutures 

 cut the posterior border of the cephalon at about the genal angles 

 and then extend inward and forward to the base of the narrow eye 

 lobes near which they curve ; in front of the eyes the sutures extend 

 forward with a gentle outward and then inward curve so as to cut 

 the front margin on a line with the sides of the front portion of 

 the glabella. 



Thorax with seven segments ; axial lobe strong and marked by a 

 short median spine or tubercle on each segment, D. tontoensis, or 

 apparently smooth, D. productus; pleural lobes with each segment 



* Specimens of the cranidium of D. succicus from the Andrarum limestone at 

 Andrarum are now in the collection of the United States National Museum 

 (C. D. W.). 



