(i) t>G Pulmontologia Slnica Ser. B 



This genus is closely related to Loxoreras, McCoy, with which it agrees in tlie 

 character of the siphunclo. Its distinctive character however is seen in the development 

 of the compound septa, or septa and pseudosepta, with stereoplasmic deposit between. 

 In these respects the genus is related to Actinoceras. Indeed this genus may be 

 considered as intermediate between Loxoceras, and Actinoceras, partaking of some 

 cliaracters peculiar to the one and of others characteristic of the other. 



The exterior of the shell is unknown except that it is not annulated. So far as 

 can be ascertained, the surface is smooth. Expansion is regular, and although the living 

 chamber is still unknown, there is no reason for assuming that it is other tlian in 

 (Mhocems. 



Genotype. Strrcojilasmoccras })scudii><e}itntii ni Grabau, Ordovician. 



It is liighly proliably that the specimen figured l)y Crick as Orflioceras or Actino- 

 rrrns (Geol. Mag. New Ser. Doc. IV. Vol. X, PI. XXII fig. A) belongs to this genus, for 

 as far as can lie ascertaine<l from the reproduction of the photograph it sh<_nvs the pseudo- 

 septa and stereoplasmic filling of S. psenihi^^eptntu'in . 



Stereoplasmoceras pseudoseptatum Grabau fsp. nov.) 



Plate VT, flgP. 5 - 7. Plate IX, fig. 11. 



Shell regularly tapering, apparently at a variable rate, thougli this may be due to 

 the variation in direction in which the sections are cut. In a specimen from Linchenii-, 

 Shantung (cat. no. 80) the rate of tapering appears to lie 1 in 6.5 while in a sectioned 

 siiccimen from Ningyang Shantung (Plate XI, fig. d eat. no. 57) it is only 1 in 12.5. 

 Still another section of an typical specimen from Tangshan (Plate \l. fig. 5, cat no. 5S) 

 shows a rate of tapering of 1 : ;).75. These variations are probably due to the fact that 

 the sections are cut somewhat obliquely and so do not give the true rate of tapering. The 

 true rate lies probably Iietween the two extremes - i.e. about 1: 9. 



Section subcircular, apparently a little flattened on one side. Septal distance 

 about 4.6 mm. (varying in the different specimens from 4.5 (rarely 4) to 4.7, the shell 

 diameter varying from 25-30 mm. but not in the same proportion). Towards the 

 apertural end in the longer specimens, tlie interval increases to 5 mm. or to a little more 

 the maximum shell diameter observed being somewliat less than 40 mm. The depth of 

 the septa is from 1 4 to 1 ^l camera. The septa are conspicuously compound, owing to 

 the numerous pseudosepta. On the upper side of the sei)tum, the pseudosepta extend about 



