^°^ ^- Grahau—Ordovician Fossils from North CJdna (i) 83 



1920 Actinoceras (Ormoceras) sp. indet. Yabe, Palasontology of Southern China, pi. XIX 

 fig. 9. (not pi. XVIII fig. 12). 



Shell large, tapering at the rate of about 1 in 5 to 1 in 5.5. Siphuncle centran or 

 nearly so, increasing very slowly in diameter, the nummuH strongly flattened above and 

 below so as to be in contact with the septum for nearly one fourth their width on all 

 sides. At a point where the shell is 24.2 mm. in diameter, the siphuncle is 8.5 mm. 

 (Plate VIII, fig. 2, cat. no. 27). In another specimen (Plate VIII, fig. 1, cat. no. 4) 

 the diameter of the siphuncle is 9.5 mm. where that of the shell is 25 mm; and 11 mm. 

 where that of the shell is 31 mm. the rate of tapering being about 1 in 20 to 1 in 22. 

 Septa regularly concave, their depth at the center being equal to 1 4 or 1 | camerte, and 

 their distance apart about 3 mm. or somewhat more, where the shell is about 30 mm. in 

 diameter. Caraerse mostly filled with stereoplasm which often has the appearance as if it 

 were deposited on both sides of the septum (See Plate VIII, figs. 2, cat. no. 27). I have, 

 however not been able to satisfy myself that this is actually the case. Instead- it would 

 appear that the septa are more or less undulating, partly so away from the siphuncle, but 

 more usually near it, where there is sometimes a marked annular depression of the 

 septum, so that it comes to lie almost opposite the ambital portion of the nummulus. In 

 other cameras again this depression is not seen, and sometimes in section one side 

 appears regular while the other shifts backwards. Commonly the stereoplasm fills the 

 camera almost or quite to the siphuncle and completely to the next succeeding septum. 

 In other cases however, where the septa maintain their normal position, the stereoplasm 

 stops before reaching the siphuncle, leaving a saucer-shaped depression around the 

 nummulus as in A. tani. 



The specimens on which this description is based, agree in all essentials with the 

 photograph of a specimen collected by Samuel Couling M. A. near Ching Chow Fu, 

 Kiao-chow, province of Shantung, and figured by G. C. Crick (loc. cit. ) on his Plate 

 XXII, fig. C. His specimen may have been larger than ours, foT the scale is not 

 indicated, but the proportions are essentially the same, the siphuncle being 15.8 mm. 

 where the shell is 47 mm. and the septa 3.3 mm. apart. Crick compares his specimen 

 with A. tenuifihom Hall of the Black River beds of North America. In that species, 

 however, the siphuncle is proportionately broader (the proportions being about as 1 to 1.9, 

 whereas in the Chinese species, they are as 1 to 2.8). The septal interval is also greater, 

 being in the American species 7 to 7.5 mm. where the shell is 27 mm. M'ide, the propor- 

 tions of depth of camera to diameter being approximately as 1 to 6.5 instead of ranging 

 between 1 to 8 and 1 to 10, as in the Chinese species, In A. tenuifilum the septa are also 



