BRITISH FOSSILS. 



Decade VII. Plate IV. 



ENCRINURUS SEXCOSTATUS. Figs. 1 to 1/. 



[Genus ENCRINUKUS. Emmrich. (Sub-kingdom Articulata. Class Crustacea. 

 Order Entomostraca. Tribe TrilobitsB or Palseadse.) Glabella inflated, clavate, with 

 3 indistinct lateral lobes, and a large forehead lobe ; eyes pedunculate, smooth (finely- 

 facetted, Kutorga) ; the facial suture posteriorly ends in advance of the head angles, and in 

 front runs above the margin; the cheeks are separated in front by a vertical suture, 

 enclosing a narrow vertical rostral shield; thorax segments 11, equal, without pleural 

 grooves, notched at the ends, but not produced into spines ; tail with the ends of the 

 pleurae free, the axis many ringed. EvKpiuos a lily-shaped animal; ovpa a tail, in 

 allusion to the resemblance between the many-jointed axis of the tail and the stems of the 

 Criuoidea.] 



Diagnosis. E. latus ; glabella antice subsphericd et ad marginem 

 frontalem fascia lata crassd circumeinctd ; genis scrobiculatis, angulis 

 spinosis ; caudd trigond, obtusd^ axi annulis crebris, per medium \{non- 

 nullis anticis exceptis) obliteratis ; pleuris 6, rarius 7, subplanis. 



Synonyms. Cybele sexcostata, Salter (June 1848), Memoirs Geol. 

 Surv., vol. ii. pt. 1. pi. 8. fig. 10 (not fig. 9). Zethus sexcostatus, M'Coy 

 (1851), Synops. Pal. Foss. Woodw. Mus., fasc. 1. 156. Encrinurus sex- 

 costatusy Salter (1852), ib. Appendix A. vol. iv. pi. 1 g, fig. 6, 7. 



We are induced to figure this trilobite, although it is not quite 

 perfect in all its parts, because it completes the illustration of the 

 same species formerly given in the second volume of the Memoirs, 

 where the tail only was figured ; and it is the more desirable to pre- 

 sent it in illustration of the genus, as the two species which are 

 best known, the E. pundatuSy and variolaris, are chiefly Upper 

 Silurian, and have been fully illustrated lately in the " Geological 

 Journal.'' 



In the general appearance, in the structure of the remarkable 

 elevated eyes and of the hypostome, the coarse tuberculation of 

 the head, — the many-jointed axis of the tail, and its few lateral 

 ribs, there is the greatest similarity to Cyhele,^ with which genus 



* Zethus of Pander and Volborth, a name which we cannot adopt, because Pander't 

 ill-defined genus was chiefly founded on a Cheirurus. 



[vii. iv.] 7 D 



