BRITISH FOSSILS. 



7 



known till we have more complete evidence tliat the var. ohesus is 

 distinct as a species from the well-known Swedish type. 



Locality and Geological Position. — Upper Lingula Flags, 

 Carreg Wen, near Berth, and Penraorfa Church, both near Tre- 

 madoc, N. Wales. Abundant at Whiteleaved Oak, Malvern, in the 

 Upper Lingula Flags (Black Shales) of that locality. 



olenus (sph^roph.) humilis. 

 Plate YIII. Figs. 9-11. 



Diagnosis. 0. {Sph.) minutus, capite angusto antice cmarginafo, 

 pleuris 7, posticis solum spinosis, cauda sexcuspidata. Glabella convexa 

 angusta parabolica, sulco basali completo, reliquis obsoletis, cei'vice spi- 

 noso. GencB convexissimce, ocidis omnino posticis, magnis. Thorax 7- 

 costatus, pleuris duobus anticis muticis, reliquis spinosis. Cauda brevis 

 semi circularise Q-spinosa, spinis externis majoribus. 



Synonyms. Olenus humilis, Phill., Mem. Geol. Surv., vol. ii, pt. 1, 

 pi. 55. Salter, Mem. Geol. Surv., vol. iii. ined. pi. 5, fig. 12. 



This minute species is well characterized by its very narrow 

 instead of wide cheeks. Yet in other respects it is a perfect 

 Sphcerophthalmus , and such a copy in miniature of the Glenoid 

 type, with nearly all the characters exaggerated or reduced, as to 

 show us that great variation is to be found within its limits, and to 

 induce us to regard the various groups into which Olenus has been 

 divided as sub-genera rather than distinct generic types. 



.Description.— A minute form, not above a quarter of an inch in 

 length, and of an ovate shape ; the head broadest, as usual in this 

 sub-genus, but rather squarish-oblong, with an emarginate front, 

 the very convex cheeks projecting on either side so much forward 

 as to bring their greatest convexity in advance of the narrow para- 

 bolic glabella ! The facial suture follows this convexity in a sigmoid 

 line, cutting the front margin at a short distance outside the axal 

 furrow, then curving outwards widely, and then again at the lower 

 third much contracted inwards to the place of the eye, which is near 

 the base of the cheek. The eye-lobe which covers it is elevated and 

 easily broken away, being divided by a deep furrow from the fixed 

 cheek. 



The eyes are large and round, and placed quite at the base of the 

 free cheeks, which are true semicircles, strongly margined, and com- 

 pletely contracted to a point behind, showing (so far as I can seo) 



