282 RESEARCH IN CHINA. 
Shell large, broader than long, subelliptical in general outline, the hinge-line 
about one-half as long as the width of the shell, the cardinal extremities rounded. 
Pedicle valve depressed-convex on the umbo, with a broad and profound mesial 
sinus toward the front, the surface of the valve anteriorly which slopes toward the 
sinus being about three-fourths of the total width of the shell; the beak rather obtuse 
and slightly incurved; the cardinal area small and apparently with rounded cardinal 
margins. Brachial valve strongly convex, most prominent along the median line, 
the mesial fold broad and scarcely differentiated from the lateral slopes; beak small, 
slightly incurved. Surface of both valves apparently smooth. 
The dimensions of a pedicle valve are: length 16 mm., width 24 mm., depth of 
valve at umbo 5 mm. ‘The dimensions of a smaller brachial valve are: length 11 
mm., width 14 mm., convexity 4.5 mm. 
The specimens from Ssi-ch’uan which have been identified with this species 
described by Martelli from southern Shen-si are all more or less imperfectly pre- 
served, but, aside from their somewhat smaller size, they seem to be identical with 
Martelli’s examples. That author seems to have been in error in referring his speci- 
mens to two distinct species belonging to different genera, since his Schizophoria 
poloi and Porambonites intercedens, judging from his illustrations alone without an 
examination of theoriginal material, seem to be based upon differences which can be 
legitimately considered only as individual variations. Furthermore, both of his 
generic references seem to be incorrect, the species being a good example of Tr1plecia. 
This species is of the general form of the North American 7. extans Emmrich 
from the Trenton limestone, but the sinus of the pedicle valve is less angular and 
somewhat broader and the fold of the brachial valve rounder and less sharply differen- 
tiated from the lateral slopes. The cardinal margins of the pedicle valve seem also 
to be rounded and not angular, as in the North American species, but this character 
can not be certainly determined in the condition of preservation of the specimens. 
The surface characters of the shell are also obscure because of exfoliation, but the 
shells seem to be smooth, except for some obscure lines of growth. 
Orthis calligramma Dalman (plate 25, figs. 3-6). 
1845. Orthis calligramma de Verneuil, Geol. Russia and Ural Mts., vol. 1, p. 207. 
1859. Orthis calligramma Murchison, Siluria, p. 209, plate 5, fig. 8. 
1869. Orthis calligramma Davidson, Brit. Sil. Brach., vol. 1, p. 240, plate 35, figs. 1-24 (in part). 
1883. Orthis calligramma Kayser, Richthofen’s China, vol. rv, p. 40, plate 3, fig. 12. 
1901. Orthis calligramma var. serica Martelli, Boll. della Soc. Geol. Ital., vol. xx, p. 297, plate 4, figs. 1-4. 
1901. Orthis calligramma var. davidsoni Martelli, Idem, vol. xx, p. 301, plate 45, figs. 5, 6. 
The specimens of this species contained in the Chinese collection agree closely 
with the typical form of the species as interpreted by de Verneuil in the Geology of 
Russia.. The dimensions of an average specimen in the Chinese collection are: 
length 8.5 mm., width 11mm. ‘They are marked by 20 to 25 simple rounded plica- 
tions, the interstices being occupied by three or four longitudinal strie. The 
pedicle valve is the most strongly convex, with the beak incurved and extending 
backward beyond the hinge-line; in none of the specimens has the cardinal area been 
observed. ‘The brachial valve is nearly flat or slightly convex and usually has a 
broad mesial flattening or slight depression. 
This species is a common and variable one in some of the Ordovician faunas of 
Europe, both in Great Britain and on the continent, but it has never been recognized 
in its typical form in the North American faunas. The specimens from eastern Ssi- 
ch’uan closely resemble, in all essential details, Martelli’s illustrations of the same 
species from Shen-si and also Kayser’s from further west in Ssi-ch’uan. 

‘Geol. Russia and the Ural Mountains, vol. 11, p. 207. 
