64 SYSTEMATIC ARRANGEMENT 



margin (the Clypeus). The eyes and facial suture cannot be distinguished. The body is pro- 

 bably furnished with eight joints (only seven rings are distinctly represented in the figure) ; 

 the rings and the lateral plates are highly arched and broader towards the posterior part ; 

 the diagonal diameter of each ring is greater than the width of the lateral lobes ; the latter 

 terminate at the margin in a spine ; the separate rings are successively broader and larger 

 towards the posterior part. 



Caudal shield large, with an almost simple, apparently unarticulated axis, upon which 

 is placed a long spine, bent backwards ; the external margin furnished with spines alter- 

 nately large and small, the sides with indistinct radial folds. The whole surface is 

 finely granulated, there are large tubercles on those parts of the circumference whence 

 spines spring. 



Locality. — In the transition limestone of the Eifel. 



The only known species is 



A. armatu», GoLDFUSS, Nova acta Pki/s. Med. Soc. Ca.s. Leap. Carol, n. cur. vol. xix, PI. I, 

 p. 355, Table XXXIII, Fig. \, a, c. Entire length two inches, the body about ten lines. 

 The granulation appears to be uniform, it forms a diagonal row of larger tubercles on the rings 

 and lateral lobes, accompanied also by smaller ones. The caudal shield exhibits radiating 

 folds, which turn towards the larger spines of the margin of each side ; between the first 

 and second of these spines there is one smaller spine, between the three following there are 

 always two ; the two most central principal spines immediately at the end have no smaller 

 spines between them. 



Second Sitbdivisio» {h). 



Ten-jointed Trilobites with a short articulated caudal axis. Animal not able to roll 

 itself into a ball. 



Genus 5. — Bronteus,* Goldf. (Goldius de Koninck). 



The caudal shields of this genus are common enough, but all the other parts are so 

 rare, that I have never had an opportunity of observing them. The character of the group 

 may possibly therefore be defective. 



The cheek-shields are always broken off from the cephalic shield, whence -Goldfuss 

 inferred their actual absence, which to me, however, does not appear probable ; the remain- 

 ing part has a highly reflexed margin both before and behind, and a depressed glabella 

 joining the margin anteriorly. The glabella is divided by lateral bent intersections into 

 four lobes, which are successively smaller from the antei'ior to the posterior part, and con- 

 tracted at the third and fourth lobe. The facial suture, which, in my opinion, borders the 

 cephalic shield on both sides, issues at the anterior part from the margin near the angle of 



*Dr. Beyrich has recently communicated additional information concerning this genus, in his 

 treatise on ' the Trilobites of Bohemia,' and has endeavoured to determine the distinction of the 

 species move accurately. He proves tliat some species possess a granulated and others a lineated 

 surface of shell, and further distinguishes them according to the number of furrows at each side of 

 the caudal .shickl, which amount to either six or seven. 



