BRITISH FOSSILS. 



5 



it has 18 body rings, and clearty belongs to a different natural 

 group, in which the cheeks are much contracted, and the glabella 

 enlarged ; in the majority of Oleni the reverse is the case. 



I believe Angelin has good reasons for supposing there are 

 several distinct genera included under Olenus, but I do not quite 

 see the way to their definition yet. The term Feltura can only 

 stand by courtesy, for it was founded on a species of Lichas, as may 

 be seen by reference to Capt. Fletcher's description of the British 

 Upper Silurian species of that genus.* 



Locality and Geological Position. — Upper Lingula Flags, 

 Carreg Wen, Borth, Portmadoc. 



OLENUS SCAEAB.510IDES. 



Plate VIIT. Figs. 1-3. 



Synonyms. Vermiciilites vagipomis, Bromkll, in Act. Lit. Upsal., 

 1729, pp. 525, 528, cum icone. Eniomostracites scarahceoides, Wahlenb., 

 Nova Act. Soc. Upsal,, vol. viii. t. 1, f. 2. Olenus scarab., Dalman, 

 Palaeadas, p. 257. Olenus scarab., Hisinc4EE, Lethaea Suecica, t. 4, f. 4. 

 Paradox scarab., Brongniakt, Crustaces, foss. p. 34, t. 3, f. 5. Pel- 

 tura scarab., Milne-Edw., Crustaces, vol. iii. p. 344 (1840). Peltura 

 scarab., Angelin, Paljeont. Suecica, pi. 25, f. 8 (mala), 1855. [Olenus 

 spi7iulosus? Phill., Mem. Geol. Surv., vol. ii. pt. 1, pp. 55, 239.] O. 

 scarab., Salter, Siluria, 2nd ed., Appendix, p. 540. 0. scarab., Id., 

 Mem. Geol. Surv., vol. iii. ined. pi. 5, figs. 2-5. 



In size, as well as form, these pressed and cfistorted Trilobites 

 agree pretty well with Christiauia specimens presented by Dr. 

 Th. Kjerulf to the Mus. Pract. Geology. But ours show only one 

 ring to the axis of the tail besides the terminal lobe. Wahlenberg s 

 fossil has two rings to the axis. The marginal spines are only 

 clearly seen in one British example ; they do not differ from the 

 Swedish species except in being shorter (see fig. 3). The glabella 

 in our specimens is broader, and the lobes less distinct. It is mani- 

 fest, therefore, that there are sufficient differences to render it 

 probable that better specimens will require us to distinguish it. I 

 shall at present call it — 



Var. OBESUS. 



The following characters appear to me to be constant, and I find 

 them both in N. W elsh and Malvern specimens. 



* Quart. GeoL .Journ., vol. ri. )». 235. 



II H 3 



