S1LUU1AK AUE. 



ARTICULATA. 



CLASS CRUSTACEA. 



ORDER t Trilobita. 



FAMILY PAEADOXID^E. 



ll<-ail \\rll developed, sometimes very large ; facial sutures generally 

 sultparallrl, especially the anterior portion; ribs each provided with a 

 longitudinal furrow. Thorax larjre, consisting of from twelve to twenty 

 -infills. J'yjridium very small, and always with few segments. 



This family includes the genera Paradoxiden, Olenus, Olenellus, Peltura, Sao, 

 >/ni/ii*, Trin rf/irits, Agraulas, EUipaocqtkdhtt, ConocorypJte, 1 and probably 

 Otoriocephalitt, Onpioephaku sod. Menoeepfalitt. It embraces a con- 

 siderable number of species, some of which attain a very large size. They are 

 jjeiierally rrmarkablc for the great development of the thorax, compared with the 

 Miiall si/e of the ])y^idiiim. The whole family, with the exception of Triarthrus, 

 seems to be mainly, if not entirely, confined to the Primordial or oldest group of 

 fossilifcrous rocks. 



Genus AGRAULOS, CORDA. 



Synon. Arinn, BARRAlcnx, Note I'n'liin. 1846, 12 (not Fenusac, 1819). 



Ilmr, CORDA, Prodr. 1847 (not Oken, 1815, nor Lesson, 1837). 



Ayraulot, CORDA, ib. 1847. 



Arionidet (BABBAKOK, MSS.), Bnosx, Index Pal., 1848, 103. 



Arioncllui, BABRAKDE, Syst. Sil. Boh. 1852. 



Crtpictphaluit (part), OWBX, Report Geol. Surrey, Wisconsin, Iowa and Minnesota, 1852, p. 876. 

 Elymnl. AXP*VAC, daughter of the Bret King of Athens. 

 Type. Arion ceticephaliu, BABBANDE. 



Entire animal more or less elongate-ovate, distinctly trilobate. Head forming 

 more than a semicircle, nearly straight behind ; glabella conoid-subovate, provided, 

 in young examples, with three or four lateral furrows, which are usually nearly or 

 quite obsolete in the adult, margined in front by a more or less developed border 

 connecting with the cheeks on each side. Facial sutures widely separated, ex- 

 tending and converging forward from the eyes so as to intersect the anterior 

 margin within a point where a line would strike it if drawn through each eye, 



Conocoryphr, Corda, 1847 = Conocephalus, Zcnker, 1833 (not Thunbcrg, 1812) ~ Conocepha- 

 lites, Barrande, 1852. 



