73 
ee eee 
The genus Chonetes is nearly allied to Producta, from which it is distinguished by its arti- 
culated valves and row of tubular spines on the margin of the ventral area, as well as by other 
characters of less importance. The spines, unfortunately, are preserved only in the smaller 
number of specimens, and thus the affinities uf a given example have often to be decided apart 
from this character. Even in the absence of this, however, Chonetes may generally be distin- 
guished with ease from Producta by the fact that the ventral valve is proportionately less 
gibbous and ventricose, and the surface striation is finer. On the other hand, the genus 
Chonetes in form and external appearance makes an approach to the genera Strophomena and 
Leptena, and it may thus be regarded as being to some extent a link between the families of 
the Strophomenide and Productide. 5 
Six or seven species of Chonetes occur in the Corniferous and Hamilton formations of 
Canada, of which one, viz., C. hemispherica has previously been recorded by Mr. Billings‘ 
and all are found in the same formations in the State of New York. 
85. CHONETES LINEATA (Vanuxem). 
Strophomena lineata (Vanuxem), Geol. Report of the 3rd District, New York, p.139, Fig. 6. 
Chonetes glabra (Hall), Tenth Report on the State Cabinet, p. 117. 
Chonetes lineata (Hall), Pal. N. Y. Vol. IV. p. 121, Pl. XX. Fig. 3. 
Shell semi-oval, the length about four-fifths of the width ; hinge-line equal to the greatest 
width of the shell, and forming about right angles with the sides of the shell. Ventral valve 
very convex, or ventricose, regularly curved from the umbo to the front, the cardinal angles 
slightly flattened. The sides of the ventral valve nearly straight and the front margin broadly 
rounded. The dorsal valve concave, the concavity being less than the convexity of the ven- 
tral valve. Area of both valves very narrow, that of the dorsal valve linear. Cardinal spines 
rarely preserved, small, slightly oblique to the hinge-line, rarely more than two or three visible 
on each side of the hingeline. Surface marked with numerous slightly elevated rounded 
strize, about ten in the space of one line, which increase in number by bifurcation and inter- 
culation in proceeding from the beak to the margin. In well preserved specimens extremely 
fine concentric striz can also be observed. The interior of the dorsal valve exhibits lines of 
pustules, corresponding with the strize outside. 
Chonetes lineata is of not uncommon occurrence 
in the Devonian Rocks of Canada, both in the Cor- 
niferous Limestone and the Hamilton formation, 
but especially in the latter. Average examples have 
a width of five lines and a lengthof about four lines. 
It is readily distinguished by its general form and 
Fig. 22, 5 
a. Ventral valve of Chonetes lineata, Hall, natural SUface characters, and it seems very probable that 
ate Bs ena! valve of the same, after Hall, enlarged the Chonetes Vandellana of Hall (Pal. N. Ke, Vol. 
and showin i i i a 5 . . 
& the cardinal spines. c. Interior of the dor iv., PL xx f Fig. 4.) is nothing more than a variety 
sal valve of the same. All from the HamiJton group. : 8 
of this species. 
Locality and formation.—Corniferous Limestone of Hagersville and Port Colborne. 
Abundant in the Hamilton Formation of Bartlett’s Mill, near Arkona, in the Township of 
Bosanquet. 
° 87. CHONETES SCITULA (Hall). , 
Chonetes scitula (Hall), Tenth Report on the State Cabinet, p. 147. 
Chonetes scitula (Hall), Pal. N.Y., Vol. iv., Pl. XXI., Fig. 4. 
Shell small, semi-oval or semi-circular, the width exceeding the length by from one-fourth 
to nearly a third (usually about five lines in width, by three and a half in length). Hinge- 
line usually not quite equal to the greatest width of the shell, generally producing rectangular 
cardinal angles. Sides nearly straight; anterior margin rounded broadly. Ventral valve 
‘convex, depressed towards the cardinal angles, sometimes regularly curved from the beak to 
the front, sometimes with a slight mesial depression almost approaching a regular sinus. Dor- 
sal valve very concave, closely applied to the convexity of the ventral valve. Area of the 
ventral valve, narrow, broadest in the middle, its plane coinciding with that of the cardinal an- 
gles. Foramen partially closed by a convex deltidium, partially filled with the cardinal process 
of the dorsal valve ; its shape broadly triangular. Dorsal area linear, about half the width 
