^0^ I- Grabau — Ordovician Fossils from North China (i) C'-l 



Genus CameroCERAS Conrad (emend. Hyatt) 

 Cameroceras styliforme Grabau (sp. nov.) 



Plate IV Figs. 4-6 



A small slender siphuncle of Cameroceras occurs in the upper or Liangchiashan 

 beds but no portion of the shell remains in the specimens so. far obtained. 



A specimen (Plate IV fig. 4) measuring 30 mm. in length, and of suboval 

 section, measures 3.5 mm. in transverse, and 2.5 mm. in dorso-vental diameter at the 

 lower end. The corresponding measurements at the upper end are 6.6 mm. and 4.8 mm. 

 respectively. The vental side is distinctly flattened. The siphuncle was evidently 

 enclosed l>y camertc. Their distance apart near the upper end, as shown by the 

 annulations, was 2.2 mm. and the angle which these annulations form with the ventral 

 line of the siphuncle is about 6S degrees. Wall of siphuncle of moderate thickness; 

 interior filled M'ith crystalline calcite, but showing in the center, at the smaller end of the 

 siphuncle, an empty endosiphocoleon of semi-lunar section, its flat base corresponding to 

 tlie flat side of the siphuncle. The width of this side is 1.3 mm. while its dorso-ventral 

 diameter is 0.5 mm. (Plate IV fig. 4b). There are three other lumens irregularly placed 

 around the periphery, but equi-distant from the outer wall, indicating that they represent 

 part of an endosiphosheath. * 



Another fragment (Plate IV, figs. 5a-c) representing a larger portion of the 

 siphuncle, measures 7.3 and 5.9 mm. respectively in lateral and dorso-ventral diameters. 

 The ventral side is not so much flattened, but is more broadly rounded than the dorsal. 

 The siphuncle at this point was not absolutely in contact with the shell, for the septal 

 edges form a distinct, broad, rounded saddle upon the ventral side. Septa 2.2 mm. apart. 

 Siphuncular wall (silicified) rather thick, the interior filled with crystalline calcite, except 

 for a central sheath of similar section as that of the wall of the siphuncle, and like that, 

 silicified. Its diameters, at the upper end are: lateral, 5 mm., dorso-ventral, 3 mm.^ the 

 dimensions of the siphuncle at this end being 7.3 and 5.9 mm. respectively. At the other 

 end, 8 mm. distant, where the dimensions of the siphuncle are 6 and 5 mm. the inner 

 tube measures 3 and 1.8 mm. respectively. Thus, while the lateral tapering of the 

 siphuncle is 1.64 mm. in 1 mm. and the dorso-ventral tapering 1.12 mm. in 1 mm., that 

 of the inner tube is 2.5 and 1.5 in 1, respectively. 



A third specimen (Plate IV figs. 6a-c) represents a still larger portion of the 

 siphuncle of apparently the same species. Its length is 13 mm., while the diameters at 



* See the foot-note on p. 38 



