48 SILURIAN TPJLOBITES. 



Locality. — Caradoc slates of Pen-y-Rhiw, west of Bala, over the volcanic ash-bed. 

 (Mus. Pract. Geology, figs. 11, 12.) The other locality given in the Decade above quoted is 

 erroneous; the specimen referred to is a species of Oyyyia, which will be figured 

 further on. 



Phacops (Odontochile) imbricatulus, Angelin ? PI. IV, fig. 10. 



[Phacops imbricatulus, Angelin, Palseont. Suec. t. vii, fig. 5, 1852. ?] 



This I do not wish yet to name. It is a new British species, but scarcely perfect 

 enough to assure me it is not the same as one of Green's published casts. 



The pygidium is seven-eighths of an inch long, excluding anymucro it may have possessed, 

 and the width about one and a half inch. It is rather flat, the centre raised in a low pyramidal 

 form, and the sides sloping outwards and gently curved down near the very narrow, regular, 

 smooth margin. We have two specimens, in both of which the axis is not one fourth the 

 entire width at tip ; it is regularly conical to within a very short distance from the margin, 

 annulated by about twelve or thirteen flattened rings, and has an appendice beyond, as far 

 as the prominent tip ; the rings of the axis are angulated forwards. The axal furrows slight 

 but distinct, the pleural furrows on the side-lobes widely patent, and nearly straight, 

 except a slight angular backward bend near their abrupt ends. There are ten lateral ribs, 

 all strongly duplicate to their very tips ; the intermediate furrows not keeping quite 

 separate, but combined at the ends, and nearly as strong as the principal ones. This strong 

 duplication gives a very striking character. The incurved margin is regular and narrow 

 all the way round. 



It is very like P. mucronatus from Sweden ; but perfect specimens of that species (see 

 woodcut, supra p. 47) show that species to have had a narrower tail with wider margin, 

 and the head is flattened, with arched lower glabella-lobes. It must be distinct. But 

 the P. imbricatulus, on the other hand, is quite like ours ; it has ten dichotomous side-ribs, 

 and a very distinct margin. The axis has ten distinct, and five or six terminal joints. 

 The tail is mucronate. Altogether it is very like our species. 



Locality. — May Hill Sandstone (Upper Llandovery), of Nash Scar, Presteign, 

 collected by Mr. J. E. Davis, of the Middle Temple. (Mus. Pract. Geology.) 



