the Palceozoic Bivalved Entomostraca. 2 1 7 



with three unequal shallow excavations), giving rise to a three- 

 lobecl cast, which has to some extent the appearance of a 

 BeyricMa. 



Individuals vary considerably in their relative proportions, 

 and in the depth of the internal excavations of the valves. 



The casts of this peculiar species occur in great numbers in 

 theWoolhope Shale near Malvern ; but amongst several dozen 

 specimens in this bed, collected by Dr. Grindrod, we have de- 

 tected only one or two with shells. In the bluish-grey lime- 

 stone, however, at the base of the Upper Ludlow beds at 

 Hales End, near Malvern, shelled specimens occur in profu- 

 sion. As above intimated, the Scandinavian specimens, re- 

 ferred to in the 'Annals Nat. Hist.' 1855, though casts, have 

 remains of the shells attached. 



Cytherellina siliqua is abundant also in the calcareous bands 

 at the base of the Woolhope beds near the Wych, Malvern ; 

 and several large specimens (which we regard as varietal, 

 var. grandis) were obtained from the engine-shaft of the rail- 

 way-tunnel at that place (fig. 1). Some were also got from 

 the base of the Wenlock Shale in that tunnel. 



Fig. 2 represents a specimen of medium size, with less 

 convex back and rather more convex sides than tig. 1 ; such 

 are not uncommon in the Aymestry Limestone at Chance's 

 Pitch, Malvern. 



Var. tersa (fig. 3) is smaller and more oblong than either 

 fig. 1 or fig. 2, but otherwise it has very much the same fea- 

 tures. It is from the Wenlock Limestone near Malvern. 



Var. ovata (fig. 4), though of relatively large size and closely 

 resembling fig. 1 in general aspect, is higher, shorter, and 

 rather less convex at the ends. It may have been an indivi- 

 dual of the other sex. From the base of the Wenlock Shale 

 in the tunnel near Malvern. 



Fig. 5 a and figs. 6 a, b, d, e, are from the Upper Ludlow 

 Limestone of Hales End, near Malvern, and have the most 

 common size and features. Fig. 6 c is from the drifted Scan- 

 dinavian limestone, found near Breslau. 



JEchmina*, gen. nov. 



Carapace-valves thick, straight at the hinge-line, rounded 

 at the ends, convex at the ventral border, and outdrawn at the 

 surface into a broad-based and sharp-pointed hollow cone, 

 which either involves all the surface, or (as far as at present 

 known) rises from the postero-dorsal or from the centro-dorsal 

 region. 



A less pronounced example of this out-drawn condition of 

 * From alxiJ-rj, a sharp point. 



