Palceozoic Bivalved Entomostraca. 345 



of the finer debris of the shales must have been lost in the 

 washing f, ^nd the small Entomostraca must have escaped 

 with it ; but there was some unwashed clay in the cases sent 

 to him, and from this and in cleaning the other fossils he 

 was able to collect a fair sample of the shale. This he care- 

 fullj manipulated, and out of the several fresh washings he 

 collected more than three thousand specimens of Entomo- 

 straca. Altogether there are between forty and fifty species 

 and notable varieties. Individuals of some of these are rare 

 and local ; others are common. The most abundant of the 

 whole ai-e those usually referred to smooth Cytlierce and Thlip- 

 surce ; BeyricMre are also common. 



Mr. John Young, F.G.S., of the Hunterian Museum, 

 Glasgow, received from Mr. Maw a packet of shale weighing 

 about ten pounds from the Tickwood beds and another of 

 about the same weight from the Buildwas beds. The clay 

 from the Tickwood beds he carefully washed ; and in a letter 

 to Mr. Vine (dated June 12, 1880) he gives the following 

 particulars : — " I weighed five pounds of the dried shale and 

 put it in water until it was thoroughly dissolved, stirred it 

 gently with the hand, poured the muddy water off, and kept 

 on washing until the water remained quite clear. When the 

 residue was dried, I found that out of five pounds weight only 

 two and a half ounces remained. This was composed of 

 fragments of still unwashed shale, a number of specimens of 

 small Brachiopods, fragments of Polyzoa, some of Trilobites, 

 a species of Conchicolites, a number of Entomostraca, and 

 fragments of other organisms." This gatliering is marked 

 25* in the list, the organisms generally agreeing with those 

 found in no. 25. 



I. Beyrichia, M'Coy, 1846. 



Beyrichia, M'Coy, Silvir. Foss. Ireland, 1846, p. 58. 



Beyrichia, Boll, Dimker und von Meyer's Palseontogr. vol. i. July 18J7, 



p. 127. 

 Beyrichia, auctorum. 



This genus is known by small, semicircular, semi-ovate, 

 and more or less oblong valves, strongly lobed by deep trans- 

 verse furrows. The amount and extent of sulcation vary very 

 much. Some unisulcate allies, formerly termed Beyricldai 

 simplices (already alluded to), of simple outline, and passing 

 into small, feebly furrowed, or non-sulcate Leperditioid 

 forms, have been separated as Primitiw. 1'he Beyrichi<je 

 proper {Jugosce) have the surface of the valves impressed with 

 t Op. at. p. 44. 



