NO. 5 CAMBRIAN TRILOBITES 383 



species it is difficult to indicate any difference of value in the thorax 

 except fewer thoracic segments. The pygidium of Bathyuriscus is 

 proportionately larger, and has a broader and flatter border. It is 

 not difficult to grade specimens of Ptychoparia that serve to establish 

 a strong connection between the two genera. We now have a num- 

 ber of species represented by cranidia which it is very difficult to 

 assign to either genus without feeling that the discovery of entire 

 specimens may make a new reference necessary. 



A group of species that are closely related to each other in form 

 of cephalon, thorax, and less so in pygidium, includes A. {?) capella, 

 A. camma, A. calenus, and A. iddingsi. They all differ from A. 

 ivheeleri in having strong genal spines on the cephalon, and longer 

 and sharper terminations on the thoracic segments. The pygidium 

 of A. {?) capella varies most widely from that of A. whcclcri. 



The small and interesting group of species from the Upper Cam- 

 brian Weeks formation of Utah, A. ? minor, A. ? gramilatus, and 

 A. ? unispinus are small in size and they have a strong genal spine 

 that is lacking in the genotype A. wheeleri. The variation in the 

 number of thoracic segments, seven to ii, is also unusual. These 

 species and those of the Upper Cambrian of the Appalachian region, 

 A. f agatho, A. ? anaxis, A. ? duris, and A. ? Horus, all appear to 

 be degenerate descendants of the large A. wheeleri type of the Middle 

 Cambrian fauna and all indicate an undetermined genus or subgenus. 



The species now referred to Asaphiscus are : 



Asaphiscus calenus VValcott, Middle Cambrian, Montana (pi. 60, fig. i), 

 Asaphiscus camma Walcott, Middle Cambrian, Montana (pi. 60, fig. 2). 

 Asaphiscus {?) capella Walcott, Middle Cambrian, Montana (pi. 59, fig. 2). 

 Asaphiscus f granulatus Walcott, Upper Cambrian, Utah (pi. 61, fig. 2). 

 Asaphiscus iddingsi Walcott, Middle Cambrian, Manchuria, China (pi. 59, 



fig. I)- 

 Asaphiscus ? minor Walcott, Upper Cambrian, Utah (pi. 61, fig. 3). 

 Asaphiscus ? unispinus Walcott, Upper Cambrian, Utah (pi. 61, fig. i). 

 Asaphiscus wheeleri Meek, Middle Cambrian, Utah (pi. 58, fig. i). 

 Asaphiscus sp. undt. (3), Upper Cambrian, Utah. 

 Asaphiscus sp. undt. (i), Middle Cambrian, Wyoming. 

 Asaphiscus ? sp. undt. (2), Upper Cambrian, Tennessee (pi. (>z, fig- 3)- 

 Asaphiscus ? agatho Walcott,^ Upper Cambrian, Pennsylvania; Tennessee 



(pi. 63, fig. 9). 

 Asaphiscus ? anaxis Walcott, Upper Cambrian, Pennsylvania (pi. 63, fig. 2). 

 Asaphiscus calanus Walcott, Middle Cambrian, Virginia (pi. 61, fig. 8). 

 Asaphiscus ? duris Walcott, Upper Cambrian ?, Pennsylvania (pi. 63, fig. 8). 



Arranged alphabetically after dividing into western and eastern series. 



