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 n 

 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 Porambowites intercedens, judging from his illustrations alone without an 

 examination of the original 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 Triplecia. 



This species is of the general form of the North American T. 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. n, p. 207. 



1859. Orthis calligramma Murchison, Siluria, p. 209, plate 5, fig. 8. 



1869. Orthis calligramma Davidson, Brit. Sil. Brach., vol. m, p. 240, plate 35, figs. 1-24 (in part). 



1883. Orlhis calligramma Kayser, Richthofen's China, vol. IV, p. 40, plate 3, fig. 12. 



1901. Orthis calligramma var. serica Martelli, Boll. dellaSoc. 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. 1 The dimensions of an average specimen in the Chinese collection are: 

 length 8.5 mm., width 1 1 mm. They are marked by 20 to 25 simple rounded plica- 

 tions, the interstices being occupied by three or four longitudinal striae. 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. n, p. 207. 



