THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY, 



[SECOND SERIES.] 

 No. 92. AUGUST 1855. 



VI. — Notes on Palceozoic Bivalved Entomostraca. No. I. Some 

 Species of Beyrichia from the Upper Silurian Limestones of 

 Scandinavia. By T. Rupert Jones, F.G.S. 



[With a Plate.] 



Amongst the small bivalved Entomostraca found in the Lower 

 Palaeozoic rocks are several species of the genus Beijrichia, for 

 the elucidation of which we are chiefly indebted to MM. Kloden, 

 Beyrich, M^Coy, and Salter. The Beyrichice occur very low down 

 in the geologic series, though they are not the first to indicate 

 the Crustacean class in the fossiliferous rocks. 



The carapace-valves of these little Crustaceans are usually ob- 

 long in shape, and rarely exceed y\jth of an inch in length ; the 

 more typical forms have their surfaces embossed with two, three, 

 or more transverse ridges or isolated protuberances. Some spe- 

 cimens in their general contour and in the arrangement of the 

 inequalities on the surface of the valve offer a distant resemblance 

 to a miniature human ear. Other varieties have smooth valves, 

 more or less indented by a transverse furrow which divides the 

 surface into two unequal parts. 



The remains of Beyrichice are met with, both as calcareous 

 carapace- valves (by far most usually separate), and as casts of 

 single valves, scattered more or less abundantly in the substance 

 of the rock or on the planes of stratification. Not unfrequently 

 they have been distorted by the movements which the integral 

 parts of the rock have suffered in the process of partial meta- 

 morphism. The carapaces themselves, generally as single valves, 

 are frequently met with in the Upper Silurian rocks of Britain, 

 though not in the Lower Silurian ; and they abound in some of 

 the IJpper Silurian rocks of Sweden. Yet our observations are 

 often necessarily limited to the casts of the exteriors and the 



Ann, ^ Mag, N. Hist, Ser. 2. Vol, xvi. 6 



