184 PEOCEEDINGS OP THE GEOLOGICAL SOCIETY, 



Journ. Oct. 1870, pi. Ixi. fig, 12), but differs from it chiefly in 

 the furrow being nearly vertical across each valve, instead of 

 following a curve. The furrow on the specimen is defined, though 

 faintly, on one of the valves, and it is marked by symmetrical frac- 

 ture on each*. The beauty of the pitted pyritous valves is striking, 

 but not uncommon, especially in Carboniferous bivalved Ento- 

 mostraca. The shape is evidently a very elongate ovate ; but the 

 borders are partly imbedded. Numerous oval flaky spots on the same 

 little slabs indicate, perhaps, other similar but obscure fossils. 

 Locality. Porth-y-rhaw : St. David's. 



3, Larval Trilobite ? PI. Y. figs. 17 «& ISf, 



LepercUtla? vexata, Hicks. Quart. Journ. Geol. Soc. vol. xxvii. 

 p. 396. 



These specimens are univalved orbicular carapaces, with a central 

 ridge, to some extent resembling Cijclus in character ; but they 

 have no transverse furrow. The little posterior lobes and the straight 

 continuance of the central ridge are peculiar as compared with any 

 published figures, but only sufiicient, I think, to indicate that we 

 have before us the larval form of some Trilobite. 



Locality. Porth-y-rhaw ; St. David's. 



4. Mr. Hicks has also sent me some specimens from the red rocks at 

 the base of the Cambrian strata in the St. David's promontoiy, which 

 he thinks belong to a new genus, somewhat allied to Cyclus. The 

 little irregularly orbicular surfaces of these natural casts rarely 

 seem to present any special features ; but in one case a slight trans- 

 verse line appears to divide the area unequally, and the anterior (?) 

 smaller portion is again traversed at right angles by a faint line. A 

 trace of granulation is the only other feature ; but nothing is present 

 to enable me to oflfer any definite opinion on these interesting relics 

 of prima3val life. 



From these rocks Mr. Hicks has also obtained specimens of an- 

 other form, to which he has given the provisional name of Leperditia ? 

 canibrensis (Quart. Journ. Geol. Soc. vol. xxvii. p. 4Ul, pi, xv. figs. 

 15-17). I have seen the specimens, a];d can only regard them as 

 undeterminable. 



EXPLANATION OE PLATES V.-VII. 



(Illustrative of fossils from the Menevian group of Wales.) 



Plate V. 



Fig. 1 . Agnostus cambrensis, Hicks. Enlarged. This specimen is more perfect 

 than the ones figured in Quart. Journ. Geol. Soc. vol. xxvii. pi. 16. 

 It was found at the base of the Menevian Group, at Porth-y-rhaw, 

 St. David's ; and it is one of the few fossils which reach from the 

 Harlech (or Longmynd Group) to the Menevian Group. 



2-4. clavidis, Salter. Enlarged. From Porth-y-rhaw, St. David's. 



5 & 6. Bm-randei, Salter. Enlarged. Obtained from the lower beds of the 



Menevian Group, at Pempleidu, St. David's. 



* Drawn rather too strongly in the figure. 



t Unversed, and the small posterior lobes not well expressed. 



