90 



P. oblong'us of the ordinary shape, but there are also some that have the 

 umbonal portion quite elongate. Especially worthy of mention is the one 

 represented by fig. 4 of plate LXX. Must it not be regarded as a form much 

 more appropriate to P. borealis than to P. ob/on^<fiis ? 



Locality . — Lo-ling-po near No-lu-ping, Tung-hu-hsien, I-chang-fu, prov. 

 Hu-pei. 



Geological Age : — The lower division of the upper Silurian (Gotlandian). 

 rjahnanclla acqitii'alvis which will be described next was found in association. 



Orthidse. 



Dalmanella, Hall and Cl\rke. 

 Dalmanella aequivalvis Davh kon sp. 

 PI. XXII., Fig. 10. 



1864-1S71. Ortliis acquii'alvis, Dami son: — Monogr. Brit. Dev. Bra- 

 chiopods, [1. 263. pi. XXX., figs. 9 and 10. 



In the orginal description of this species, Davidson called it an Ortlus. 

 According, however, to the more recent palaeontologi.sts, the genus is sub- 

 divided into several different groups each of which denoting an independent 

 genus. On examining the fossil, as well as the definitions of these genera by 

 various authors, the writer is led to place it in the genus Daluianclla. It has 

 a remarkably rounded contour and the surface of the shell is ornamented with 

 VK^xy fine radial striae. Besides, in both the valves the area is not very con- 

 spicuous, as is usually the case with Dalmanella . The valves are almost 

 equally convex too. 



This species is represented by only one example, which, however, has 

 comparatively well retained its outward characteristics. It has also the pecu- 

 liar shape that is characteristic of the species. The diagnosis given by David- 

 son long ago, though brief, holds excellently good with the Chinese fossil 

 under examination. It is as follows : — " Shell almost circular, broadly 

 rounded anteriorly, as well as at the cardinal extremities. Valves almost 



