OF THE SPECIES. 97 



spine is twice as long as the spine of tlie last joint of the body. The wliole upper surface 

 is granuhitcd. 



Remark. — The lateral angles of the cephalic shield are wanting in Ilfhiiughaus's otherwise very 

 beautiful figure, and the hody appears to be thirtcen-jointed ; but the perfect specimens, which were 

 intrusted to me for examination by my colleague M. Germar, had the proportions I have stated. I 

 likewise recognized in them their identity with three fragments in Sack's collection. 



14. Pit. stellifer : Scuto capitis in medio margiuis antiei acuto, angulis posticis longissime 

 productis ; scuto caudie undecies radiato. Long. IH". Tab. IV, Fig. 8. 



Zoc. — An ash-gray hmestone of the Eifel, according to specimens in Sack's collection. 



The cephalic shield, of which I have a pretty perfect specimen before me, resembles 

 perfectly that of the preceding species, but the arjterior lobe of the glabella is comparatively 

 larger, and the entire shield therefore a little longer ; the proportions of both species seem 

 to be the same in other respects. I am only acquainted with fragments of the joints of the 

 body, and can therefore onl}^ state it as probable that they terminate in lateral spines. Of 

 the caudal shield I have three specimens before me, which admit of being generally charac- 

 terized. It is comparatively smaller than in the preceding species, the axis is only divided 

 into five distinct joints at the anterior part, the joints afterwards are certainly still visible, 

 but the articulation is indistinct (at the sides we may still distinguish six segments). Five 

 ribs issue from the anterior joints to the circumference, which is upturned much as in 

 the preceding species, but the spines issuing from it are all of equal length, compa- 

 ratively much shorter and thicker, and they meet together at their bases, and between the 

 two most posterior ones there is another but odd eleventh spine, which exactly fills up 

 the gap. 



Remarks. — 1. The caudal shields represented by Wahlenberg (Nov. act. Ups. viii, 30, 5, Tab. II 

 Fig. 4) and by Brongniart [Crust, fossil. PI. Ill, Fig. 7) perhaps also belong to this species ; Dalman had 

 before suggested that these did not belong to the head represented with them {Palaad. 66, 5). 



2. Peltura BucMandi, Milne Edw. [Cr. iii, 345, 1, PI. XXXIV, Fig. 12), which perfectly cor- 

 responds with Brongniart's figure {Cr. fossil. PI. IV, Fig. 9), perhaps likewise belongs to this species; 

 I cau certainly count eleven rings at the left side of both figures, and almost thirteen at the right 

 side ; the central terminal spine decidedly seems to be in favour of its affinity with Phac. stellifer. 



Trilobifes capable of rolling themselves up, having the axis of the body diminishing posteriorly, 

 and their facial suture extending to the piosterior margin of the cephalic shield. 



The Trilobites of this group are rare, and belong to the middle and newer Palceozoic 

 strata, more particularly to the Devonian rocks, but extending as far upwards as the 

 carboniferous limestone. The number of the body rings varies from nine to twelve, 

 and may vary in the species of one genus. The glabella is very convex, but divided 

 only into indistinct lobes or furnished with slight lateral furrows. The axis of the 

 body is very gibbous, and furnished with short articulations ; the caudal shield likewise 

 possesses a distinctly articulated axis, and radiated lateral furrows or lobes. 



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