66 
valve concave and little separated from the opposite valve, whose curvature it 
follows. Area almost linear. The surface of the ventral valve is ornamented 
with concentric growth lines, a little wavy, often irregular, as well as a large 
nmnher of elongated tubercles, fairly generally arranged in quincunx and 
acting as the base of very line spiniform tubes. A line of these tubercles 
usually exists along the hinge margin. The surface of the dorsal valve is 
provided with growth lines similar to those that ornament the ventral valve 
and small furrows corresjoonding to the tubercles of the other. 
Dimensions. — Length, twenty-live to thirty millimetres ; breadth, 
twenty-seven to thirty-three millimetres ; thickness, three millimetres. 
Ohservation. — It seems to me very probable that several of the species 
described by Mr. J. Hall under the generic name Productella are in reality 
only varieties of this form, in which the ornamentation varies to such an extent 
that it is difficult to find two specimens exactly alike one another ; but as I 
have not at my disposal the necessary material to enable me to speak definitely, 
I prefer to leave the discussion of this question to others. 
Horizon and Localities.- — This species is rather common in the Upper 
Devonian of England and Bslgium. Mr. W. [B.] Clarke has sent me a single 
specimen of it, collected from a yellowish-white phtanite at Kempsey. It is 
associated with Choncles Hardrensis, Phillips. 
Genus — CHONETES, Fischer de TFaldheim. 
1. Chonetes Haedeensis, J. Fhillips. 
Orthis Hardrensis, J. Phillip?, 18 il, Pal. Foss. Cornwall, p. 138, pi. 58, fig. 104, and pi. GO, 
fig. 104.* 
Leptcena {Chonetes) Ilardrensis, McCoy, 1855, Brit. Pal. Foss., p. 454. 
Chonetes Hardrensis, T. Davidson, 18G4, Mm. Brit. Dev. Brach., p. 14, pi. 19, fig. G, 7, 8 
ififj. ccdt. exch), non Idem.., Mon. Brit. Carb. Bracli., p. 18G, pi. 47, 
fig. 12-lG. 
Shell transverse, snbsemicircnlar, cardinal line straight, angular or 
slightly rounded at its extremities. Each of the two valves possesses a narrow 
area of triangular shape, very elliptical ; the area of the dorsal valve is a 
little higher and consequently more appreciably triangular than the opposite 
