PLATE V. 



Lower Ordovician Cephalopoda: Pelintzc Limestone. 



Draiuings ly K. C. Liu 



Cldhlioceras nathani Grabau .................................................................................. p. 48 



A group of three individuals, natural size, all with their upper or dorsal surfaces exposed, 

 and all more or less worn. The rock has also been subject to slight deformations; two fracture 

 lines with slight faulting are shown, the fractures having been filled by calcite veins. The left hand 

 specimen shows only a portion of the blade, but the central one shows a large part of it. The lateral 

 alveoli in this specimen are not preserved, not extending back so far. They are however shown , 

 though in a somewhat crushed condition, in the right hand specimen (see the front view of this on 

 plate I. fig. 10). There is a difference in the rate of tapering of the two most perfect specimens, 

 also in the annotations, and perhaps, though this can not be said with certainty, in the conforma- 

 tion of the endocone. More perfect material may demonstrate, that two distinct species are 

 represented. 



On the underside of this rock-mass occurred the specimen of this species figured on plate 

 IV fig. 13, and the sections of which are shown on plate II figs 11 & 12. This specimen lay in the 

 same position as those here shown so far as the dorso-ventral surfaces were concerned, and therefore, 

 being on the under side of the slab, exposed the ventral side. Its longitudinal axis was however 

 transverse to (hose of the specimens here shown. In its detailed character it corresponds closely to 

 the right-hand specimen of the group on this plate. As it is also the specimen which has furnished, 

 in its sections, the details of internal structure, from which the models (Text figs 2 to 5) are 

 constructed, it must be considered the genotype, in case the specimens here shown prove to represent 

 distinct species. The middle one in tbat case will be a new species. 



The outer zone of the middle specimen is formed apparently by a succession of endosheaths 

 which were closely crowded in the apical part of the siphuncle. The inner part, become porous 

 from weathering, represents a solid mass of stereoplasm (organically deposited lime) apparently 

 without further endosheaths until the final one is reached. 



Peilintze limestone, Pei-Lin-Tze, Shih-Mun-Chai region near Chingwangtao, eastern Chihli. 

 (Cotype, Collected by F. F. Mathieu and presented to the collection of the Geological Survey of 

 China, Cat. No. Ill) . See further plates I, II, & IV. 



11(5 



