326 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



as far as known are essentially the same as Corynexochus. The 

 surface of the test of C. {Bonnia) parvulus is punctate and marked 

 by irregular, inosculating, very fine ridges or raised lines that are 

 arranged more or less concentrically about the highest part of the 

 glabella, also about the node on the occipital ring. (See pi. 57, fig. i ; 

 pi. 64, fig. 6.) 



The associated pygidia have the anterior border extended into a 

 short spine at the antero-lateral angles and the axial lobe has only 

 two well-defined rings. 



Although there are large numbers of the cranidia and pygidia of 

 the species parvulus, nothing is known of the thorax. The associated 

 free cheeks have a rather strong genal spine. 



Matthew refers the species parvulus to Dorypyge,'' but a compari- 

 son with the genotype of Dorypyge shows that while the glabella is 

 somewhat similar,' there are differences in form and surface mark- 

 ings and the associated pygidia are quite unlike. The test of Dory- 

 pyge is dense and granulated and that of Bonnia is punctate and orna- 

 mented with elevated lines or fine sharp ridges or granulated. The 

 spines at the end of the anterior border of Bonnia can hardly correlate 

 the pygidium with that of Dorypyge. For comparison, figures of the 

 genotype of Dorypyge are illustrated on plate 64, figures 7, ya-c. 



The species now referred to the subgenus Bonnia are : 



Corynexochus {Bonnia) parvulus (Billings) (pi. 57, %• O, Lower Cam- 

 brian. 



Corynexochus (Bonnia) busa Walcott (pi. 60, fig. 3), Lower Cambrian. 



Corynexochus (Bonnia) fieldensis Walcott (pi. 57. fig- 4), Lower Cambrian. 



CORYNEXOCHUS (BONNIA) BUSA, new species 



Plate 57, fig- i«; plate 60, figs. 3, 3a-c 



This species is represented by specimens of the cranidium and 

 associated pygidium, the surface characters of which are similar to 

 those of the pygidium. The cranidium is similar in form to that of 

 C. (Bonnia) parvulus except that the fixed cheek is narrower and 

 three pairs of short glabellar furrows are to be seen by the unaided 

 eye. 



A small median spine appears to have been broken ofif of the 

 occipital ring. 



The most striking difference is the granulated outer surface of the 

 test on both the glabella, fixed cheeks and associated pygidium ; this 



' Trans. Royal Soc. Canada, 2d ser., Vol. 3, Sec. 4, 1897, p. 197. 

 'See Dorypyge richthofeni Dames, figs, i, la-c, pi. 8, Research in China, 

 Vol. 3, Cambrian Faunas of China, 1913, Carnegie Inst, of Washington. 



