Dr. Wheelton Hind — British Carboniferous Ooniatites. 449 



Foord & Click, Cat. op. supra cit., refer doubtfully some specimens, 

 said to be from Halifax, to P. virgatus; they remark, "De Koninck 

 saj^s the ribs are not dichotoraous, but they certainly are in these 

 specimens up to a diameter of 16 mm." These shells most probably 

 belong to the species uuder description. The species alters its habit 

 with age. In the young the shell is much more globose and the 

 ribs more transverse than in the adult, when the shell is more 

 discoidal and compressed and the ribs sinuously curved on the side 

 with a deep peripheral sinus. 



The young stage may be confused with some forms of G. heyrichi- 

 amcm, but the umbilicus in the latter is much wider and inclusion 

 less. The transverse ribs less close and more acute. 



Pericyclus impressus, de Koninck, 1880. (PI. XVI, Figs. 8-10, 12.) 

 Ann. Mus. Eoy. d'bist. Nat. Belgique, torn, v, pt. ii, p. 118, pl. xlix, fig. 3. 



Specific Characters. — Shell subglobose, involute, umbilicated. 

 Whorls six, inclusion extensive, somewhat obtusely lunate in 

 sections not very high. Umbilicus large and open in the young 

 stages, becoming narrow with age ; its border rounded, sides convex ; 

 the periphery convex. 



Body-chamber occupies the last whorl. Cameraa four to a 

 quarter of an inch. Suture as drawn below (PI. XVI, Fig. 125). 



Test thin, with many simple transverse subangular ribs, the sulci 

 between which have numerous fine spiral lines. On the periphery 

 the ribs have only a suspicion of a hyponomic sinus. 



Dimensions. — Fig. 9, PI. XVI, measures, diameter 18 mm., trans- 

 versely 10mm. 



Locality^ — Millstone Grit Shales (Sabden Shales). Gill beck, near 

 Cowling, Yorkshire. 



Observations. — De Koninck's types were obtained from Veve, 

 assise iii<^. The umbilicus at once distinguishes the species from 

 others of the genus. 



In the young the ribs are much less numerous, and the umbilicus 

 wide, inclusion very small (PI. XVI, Fig. 10). 



All the specimens obtained were fron^ one bullion in shale, a quarter 

 of a mile above Stonehead Farm. 



Pericyclus virgatus, de Koninck, 1880. (PI. XVI, Fig. 7, 7a.) 

 Ann. Mus. d'hist. Nat. Belgique, tom. v, pt. ii, p. 118, pl. xlix, fig. 4. 



I have two fragments of the body-chamber and one crushed 

 example of this species from the Hedesdale ironstone. 



In ids description de Koninck says, " Umbilie assez etroit a bords 

 anguleux et infundibuliform," but his figure shows a moderately 

 sized umbilicus with a convex border. The ribs are more numerous 

 and flatter than in P. funatus, Sow., and less flat and less regularly 

 dichotomous than in P. divaricattis, Hind. De Koninck's specimen 

 was obtained at Vise. < 



Pericyclus kedesdalensis, sp. nov. (Pl. XVI, Figs. 13, 13a, 135.) 

 Specific Characters. — Shell moderately inflated, sides flattened. 

 Evolute, umbilicus about T6"in- in diameter, greatest thickness half- 

 way between the periphery and umbilicus. Inclusion extensive. 



DECADE VI. — VOL. V. — NO. X. 29 



