ILLtENUS. 



199 



Oculi longi, gJahellce vicini, d cervice vix dimidium dlametri eorum distantes. Gena 

 triangulatcB, angulis productis nec acutis, hand spinosis. Thoracis cuvis pleuris vix latior, 

 pleuris anticis deflexis. Reliqua ahsunt. 



This pretty species may or may not belong to Illamis proper. It is more depressed 

 than other Lower Sikirian forms, and the front margin is suddenly incurved. The eyes are 

 long, not broad, and gently curved, and with the lentiferous area convex. They are placed 

 so near to the posterior margin as to be about half their length away from it ; but being of 

 considerable size for the genus, they reach about halfway up the head. The eye-lobe is 

 depressed, and there is no furrow under the eye itself. The glabella is less than a third 

 the width of the head ; the axal furrows, sigmoid in shape, rise up to the level of the 

 front of the eye, and do not converge so much as our figure makes them. Our enlarged 

 figure 8 « is still a little further defective, as representing the eye too forward. Fine, 

 concentric, wavy, continuous lines ornament the whole head, but are most conspicuous 

 and coarse around the inflected front margin. 



Only parts of three front body-rings are present. Their axis is a little Avider than 

 the recurved pleurae, which are bent down and backwards from the approximate fulcrum, 

 and appear to have rather an attenuated form and oblique apices. They are longi- 

 tudinally striate. 



It is with some doubt that I add fig. 9 to this species ; it has a proportionately still 

 larger eye, -and a squarer cheek-angle, not so much produced as in the small form. But 

 these may be characters due to age, and there is no other species to compare either with ; 

 so I leave it. It is worth figuring, at all events. 



Locality. — Caradoc or Bala Limestone, Chair of Kildare, Kildare ; quoted as 

 Llandeilo in the 'Decade,' as the Bala Limestone was formerly not known to be the 

 exact equivalent of the Caradoc, but supposed to be the Llandeilo Limestone, until the 

 fossils disproved it. (Mus. P. Geology. Only these two specimens are known to me ) 



Ill.enus Rosenbergii, Eichicald. PI. XXIX, figs. 2 — 6. 



iLLiEXUS RosENBEEGii, Eichwald, Geogn. Zool. per Ingriam, Tril. Obs., &c., t. iii, 

 fig. 3 (?), 1833. 



— _ Salter. Mem. Geol. Surv., vol. ii, part 1, p. 338 (not plate), 



1849. 



— — M'Coy. Synopsis Wooclw. Mus., p. 172, 1852. 



— MuRCHisoNi, Salter. Id., Appendix, pi. i g, figs. 33 — 35 (not of Decade 2, 



Geol. Surv., -which is the true II. Murchisoni) : see p. 201, 

 1852. 



11. {IL) 4 — 5 uncias longus, gibbus, inth granuloso-striahis, capite valde convexo 

 longitudine caudam rotundatam superante, fhorace longo. Caput semiovatum, convexissi- 

 mum, f route gibba impendente, stdcis modicis subrectis, tertias longitudinis capitis efficienti- 

 bus. GencB majores verticales. Oculi minores, hand distantes, d glabella dimidio lati- 



