Vol T. Grabau Ordovician Fossils from North China (i) 77 



the development of crystalline calcium carbonate of inorganic origin in portions of the 

 carm-iv', especially on one side of the siphuncle. Pseudosepta generally define the 

 stereoplasm. Some camera? were however empty, having been filled by the matrix only 

 (a fine brownish calcilutyte) which also fills the median tube. 



Only traces of the shell are preserved which appears to have been rather thin, 

 and marked by more or less flexuous longitudinal strise. 



In a fragment of a smaller (younger) individual from the same locality (Plate 

 IX, fig. 8) the sides are more sharply acute (slightly accentuated by pressure in the 

 specimen), while the siphuncular nummuli are proportionately larger and have a nearly 

 circular transverse section. The dorso-ventral diameter of the interior of the shell (the 

 septate stone-mold) at the largest end preserved, is 24 mm., and its transverse diameter 

 about 34 mm. while the corresponding diameters of the sipliuncle are 9 and 10 mm. 

 respectively. The depth of a single camera in this specimen is 12 mm. where its short 

 diameter is 22 mm. The septal interval at this stage is slightly smaller than usual, 

 being on the average 3.33 mm. 



Because of the oval transverse section of the shell, the specimens practically 

 always lie upon one of their broader sides, and hence the weathered sections always 

 expose the transverse diameter of the shell, and the tapering seen is that of the lateral 

 largins, and hence the greater of the two. A dorso-ventral section, if obtained, would 

 show a very different rate of tapering, and a much narrower shell. The great depth of 

 the camene would however appear in such a section as well. 



A larger specimen of this species from Tangshan (Plate VII, fig. 1), is 111 mm, 

 long but incomplete at both ends. At the widest part preserved, it is 4G mm. in width, 

 while at the lower end it is 24 mm. wide, the distance between these points being 66 

 im. This gives a rate of tapering of 1 mm. in 3, essentially the same as that of Freeh's 

 figured specimen. The diameter of the siphuncular nummuli in this wider part is about 

 16mm., or about one third the width of the shell. In the lower part it is about 13.5 

 mm., and therefore more than half the width of the shell. 



The septa are about 3.8 mrn. apart in the upper, and 3.6 mm. in the lower part. 

 In a specimen on the same slab with the one just described, the interior of the siphuncle 

 is well preserved (Plate VII, fig. 3). This shows that the secondary deposits at the 

 inner ends of the septa are not continuous all around the siphuncle, but form a series of 

 rounded thickenings, there being about six of these to the circumference, judging from 

 the number shown in the specimen, which is one longitudinal half of the shell. This 

 accounts for variation in thickness of these inner deposits, as observed in different 



