158 
ventral valve is regularly arched, not sinuous, and generally rather longer 
than broad ; its beak is small, and barely projects over the hinge line ; the 
exterior surface is irregularly covered with elongated tubercles serving as bases 
for short tubular spines ; by their elongation these tubercles often transform 
themselves into true, longitudinal, irregular, rugose ribs. The dorsal valve is 
very concave, and approaches very near to the ventral valve, following its 
contour, and having its ornamentation as a cast. 
Dimensions. — The three Australian specimens under my examination 
average only ten millimetres long by eight broad. One belongs to the variety 
figured by me under the name P. gryphoules (P. Youngianus of Mr. T. 
Davidson), and the two others to the tyjie described by Martin. 
Horizon and Localities. — This species is very widespread in the Car- 
boniferous Limestone, and it is always more abundant in the upper than in 
the other beds. Mr. Toula has lately seen it among the fossils from Hofer, 
one of the Barent Isles. Mr. W. B. Clarke found it at Colocolo, and also at 
Pallal, on the Gwydir Biver. 
Qenus — CHONETES, G. Fischer de Waldheim. 
Chonetes papilionacea, J. Dhillips. 
p], X, Pig. 6. 
Dectinites jlahelliformis, Lister, 1688, Hist. Conchyl., Ill, pi. 473, fig. 31. 
Droductus latissimns, Dilhvyn, 1823, Index to the Hist. Conch, of Lister, p. 24 (non 
Spirifera papilionacea, 
Chonetes ,, 
Delthyris ,, 
Orthis ,, 
Leptcena multidentata, 
„ papyracea ? 
Chonetes ,, 
Sowerby) . 
J. Phillips, 1836, Geol. Yorkshire, II, p. 221, pi. 11, fig. 6. 
L. G. de Koninck, 1843, Descr. Anim. Poss. Terr. Carb. Belg., 
p. 212, pi. 13, fig. 5, and pi. 13 bis, fig. 1. 
A. Pahreukohl, 1844, Bull. Soc. Imp. Nat. Moscou,XVII, p. 788. 
McCoy, 1844, Synop. Poss. Ireland, p. 125. 
Idem, 1844, ihid., p. 120, pi. 20, fig. 8. 
Idem, 1844, ihid., p. 120, pi. 20, fig. 2. 
E. de Verneuil, 1845, In Murchison, de Verneuil and de Key- 
serling, Russia and the Ural Mts., II, p. 241. 
