358 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



Dr. Fritz Freeh * says of Dolichometopus and allied genera : 

 " Niohe is directly connected with Dolichometopus {Dol. suecicus 

 Ang., Tril., Taf. 37, fig. 9), as Brogger already conjectured. Doli- 

 chometopus is identical with Bathyuriscus Walcott. The American 

 recognized species with complete specimens accord with Asaphidae 

 in respect to the size of the pygidium, the course of the facial sutures, 

 and the number of rings (8). Also Symphysurus is to be traced 

 down from Dolichometopus." 



On text plate B, facing p. 39, he places Ogygopsis klotzi (Romin- 

 ger) and Bathyuriscus occidentalis Matthew in the genus Dolicho- 

 metopus, although he leaves Matthew's Bathyuriscus pupa (a probable 

 synonym of Bathyuriscus occidentalis) under the genus Bathyuriscus. 



Dr. Th. Lorenz ^ concludes that Bathyuriscus is a subgenus of 

 Dolichometopus. He says : " The genus Bathyuriscus is without 

 doubt closely related to the Swedish genus Dolichometopus Angelin. 

 The difference consists in that Bathyuriscus has a stronger relief, 

 deeper glabellar furrows, and on the back part of the fixed cheeks 

 a ridge, which is produced by the posterior course of the facial 

 suture. Dolichometopus has a perfectly flat, furrowless glabella ; 

 furthermore the facial suture extends from the posterior eye angles 

 quite direct fo the posterior border without cutting out a narrow 

 ridge as in Bathyuriscus. There is also a difference between the 

 two genera in the position of the eye curves. The cause of this is 

 that in Dolichometopus the posterior eye angles are situated farther 

 from the glabella. Despite all this the form relationship of the two 

 genera is very close, so that I hold Bathyuriscus as a subgenus of 

 Dolichometopus, as Matthew did. Equal rank for the two genera, 

 as Freeh has done in his Lethaea, I cannot commend. It is further 

 worthy of note that the related genus Dolichometopus is a guide fossil 

 [Leitfossil] for the uppermost Middle Cambrian in Sweden." 



He then compares D. acadicus Matthew and his own Bathyuriscus 

 asiaticus Lorenz and says : " Herein the generic distinction between 

 Dolichometoptis and Bathyuriscus finds expression. They agree in 

 the two semicircular eye lobes, the erect position of the eyes, the 

 club-shaped glabella flattened towards the front and the flat occipital 

 furrow. The shell structure in both is of the finest granulation. 

 Nevertheless identification of Dolichometopus acadicus Matthew and 

 Bathyuriscus asiaticus is not therefore permissible." * 



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



^ Zeitschrift der deutschen geologischen Gesellschaf t, Vol. 58, Pt. 2. 1906, p. 74. 



' Idem, p. 75. 



