(ii) 56 Palffontologia Sinica Ser. B. 



Septa strongly concave. They are widely separated, and slightly increase in 

 distance apart toward the outer chamber. The concavity is about equal to one third 

 of a camera which has a depth of i6 mm. in the last camera and 15 mm. in the next 

 preceding one, while the dorso-ventral diameters of the tube at the corresponding stages 

 are 20 mm. and 18 mm. respectively. 



Siphuncle excentric, nearer to the center than to the side. It is encircled by the 

 septal necks, which contract at the septa and gradually enlarge backwards, extending 

 to a distance of about one third the septal interval. Transverse section ovately elliptical. 

 It has a longer diameter of 3 mm. and a shorter of 2 mm. At the same place the shell 

 measures 17. 5 mm. and 17 mm. in the dorso-ventral and transverse diameters. 



The test is well preserved, having a thickness of 0.5 mm. The surface is marked 

 by coarse, transverse, elevated, flexuous lines of growth, 6 in the space of 5 mm. On 

 close examination under the magnifier we find that either the elevated ridges or the 

 depressed interspaces are wholly composed of the fine striie, slightly arching forward on 

 the dorsal side. 



Comi*arison: It is similar to the preceding species in all respects except in its 

 striking surface ornamentation. This species may be compared with Orthoceras pleuro- 

 tomum Barrande,' but differs from that by its gradual increase of septal distance and 

 by the character of the transverse undulating strife. It may be distinguished from 

 Orthoceras thyrsus Barrande^ by the fact that the latter has a circular section of the 

 shell, and the oblique, straight striae on its surface. 



Horizon and Locality: From the bed immediately underlying the red Hmestone 

 at the region not very far from He-chiao, Chung-yang-hsien (C. Li and W. P. Shu Coll.) 



Orthoceras suni Yii (sp. no v.) 

 Plate v.. Figs. 8a-b, 9. 



Shell straight, cylindrico-conical. Transverse section subslliptical. The only 

 preserved part is the apical portion of 82 mm. in length, gradually expanding toward 

 the apertural end. Mature phragmacone and body chamber not preserved. Apical 

 angle 20°. Rate of incrase about one millimeter in a length of four millimeters. 



1. Barrande: Syst. Sil. de la Boheme, Vol. II, Texte III, 1874, P-4i2, pi. 224, pi. 296, pi. 366. 



2. Barrande: Syst. Sil. de la Boheme, Vol. II, Texte III, 1874, P.555. pl- 405, figs. 15-18. 



