ENGLISH UPPER SILURIAN OSTRACODA. I39 



fine amber tint, and a few are snow-white. The 

 new genera have thus been defined: 



Bollia, Jones and Holl. 

 "In these Beyrichian Entomostraca the valves 

 have two lobes meeting below with a thin curved 

 isthmus. They have also a marginal ridge, some- 

 times unequally divided ventrally. By the lessening 

 of the lobes and the increase of the marginal rim 

 some forms seem to show a passage into Kirkbya. 

 The simple horseshoe swelling on the valve differs 

 as much from the three-lobed and the plurijugate 

 Beyrichice and from the corrugate form or Klcedenia, 

 that we propose to give this a generic standing as 

 Bollia, in honour of the late Dr. Ernst Boll, of 

 Neubrandenburg." 



Kloedenia, Jones and Holl. 



Belongs to the BeyHchice corrugatce. The main 

 portion of the valve is smooth and convex, sulci 

 very short, mid lobe small but prominent, and reach- 

 ing to the dorsal edge. It is bordered by a marginal 

 rim. 



Strepula, Jones and Holl. 



"The carapace- valves are slightly convex, sub- 

 oblong, Avith rounded ends, or semi-elliptical, that 

 is, less boldly curved at one end than at the other, 

 and bear narrow often trenchant ridges. These are 

 sometimes concentric with the lower margin, in 

 other cases partly concentric and partly irregular. 

 They run into the slightly thickened dorsal margin. 

 The intervening furrows form broad valleys, and a 

 subcentral tubercle, or even a lobular swelling, is 

 sometimes present. The chief ridge is a free supra- 

 marginal lamina, standing outwards and downwards, 

 and hiding the real marginal edge in the side view. 

 The edged view of the bivalved carapace is narrow- 

 ovate, cross-barred at the sides with ridges, some 

 straight and parallel, some oblique and divergent." 



(Lat. Strepa, a stirrup.) 



