31 8 RESEARCH IN CHINA. 



Chonetes aff. C. flemingi Norwood and Pratten. 

 Plate 29, Figure 10. 



The subject of this description is a single specimen which has a width of 7 mm. 

 and a length of 6 mm. The shape is semicircular, the convexity high, the beak large 

 and projecting, the umbo inflated, and the ears rather large and depressed. The 

 sinus is narrow and obscure. The number of spines is not known. About 1 1 ribs 

 occur in the space of 2 mm. As the shell is exfoliated the surface details can not be 

 determined. A very small area which is fairly well preserved, however, seems to 

 show that the ribs were narrow and sharp, with relatively wide, rounded interspaces. 



This specimen is unusually long for its width, and probably does not show the 

 average dimensions of the species. It much resembles Tschernyschew's figures of 

 C. flemingi Norwood and Pratten, especially figure 10 of plate Lvi. 1 Typical C. 

 flemingi differs in having a more distinct sinus and probably in the character of the 

 surface ornamentation, although only an imperfect comparison is possible. 



With the specimens from which the above description was taken occurs another 

 very young example, which possibly may not represent the same species. 



Locality and Horizon. Pennsylvanian ; Yon-yi-ssi', Shan-si (station 20). 



Chonetes sp. 

 Plate 29, Figure n. 



Of this species our collection contains four specimens, two from station 69 and 

 two from station 17. Only one specimen from each lot is sufficiently perfect to 

 serve in drawing up a description. The following characters are found in the example 

 from station 17, a ventral valve. 



The width is 6 mm. and the length 3.5 mm. The shape is subsemicircular, 

 flattened in front. The convexity is rather low and the umbonal region slightly 

 inflated. The sinus is broad and faint, or possibly absent altogether. The number 

 of cardinal spines is unknown. The ribs come about seven in 2 mm. While quite 

 distinct, they are nevertheless unusually broad and low. There are in addition 

 fine concentric striae, which are also faint. 



The specimen from station 69, likewise a ventral valve, resembles in a general 

 way that just described. The size and configuration are about the same, except 

 that the width is proportionately less. The striation is equally fine, but the ribs 

 appear to be somewhat more strongly elevated. Although it is possible that the 

 two forms do not belong to the same species, the characters shown are not sufficient 

 to warrant their separation. On the other hand, it is possible that the form allied 

 to C. flemingi may be specifically the same as the present, the difference of shape, 

 convexity, and surface being the result of individual variation or the effects of 

 preservation, such as, for example, compression. This does not seem to me suffi- 

 ciently probable, however, to warrant adopting this interpretation. 



Under this title also has provisionally been placed a specimen from the cherty 

 beds of vShan-tung (station 59). It shows the mold of the interior of a dorsal valve. 

 The width is only about 3.5 mm. and the length about 2 mm. The cardinal line 

 is equal to the greatest width below, the shape being subsemicircular, somewhat 

 flattened at the sides and front. There are about 20 rows of internal spines, indi- 

 cating a corresponding number of ribs, the distance between the rows being about 

 as in specimens from station 69. Areas near the cardinal line upon both sides, 

 including in all about one-third the entire surface, are smooth. 



'Mem. Comite Geologique [Russia], vol. 16, No. 2, 1902. 



