ADDENDUM TO THE CYPRIDINAD.E. (See page 43). 



2. Philomedes elongata. Sp. nov. Plate VI, figs. 1 a, b, c. 



Carapace-valve elongate, depressed ; long-oblong ; straight dorsal, and rather convex 

 ventral margin, with one end (posterior) elliptically rounded, the anterior truncate and 

 hooked, the straight dorsal margin being produced into a large blunt hook, overhanging 

 a deep open notch, which reaches upwards for about four fifths of the height of the valve. 

 The postero-ventral ellipticity gives the outline the shape of a broad knife-blade. If 

 compressed by embedment in the shale, this carapace may have been subcylindrical 

 originally. 



The length, including the hook, is 6 millimetres ; the hook is about ^th of the 

 whole length ; the greatest height of the valve is 2^ mm. 



The surface that remains shows numerous conspicuous radiate markings, analogous 

 to those seen in Cypridina radiata, J. and K., p. 14, PI. V, figs. 6 d, e ; also in some 

 Beyrichian casts, from the Carboniferous strata in Dumfriesshire, which belong to 

 B. gigantea, J. and K., PI. IV, figs. 27, 28. These radiate spots appear to have some 

 relation to the radiate tops of the transverse columns, dividing the blood-canals in the 

 mantle or investment of the test of Estheria, as described and illustrated by E. Grube, 

 ' Wiegmann's Archiv fiir Naturgesch.,' 1865, p. (15) 217, pi. 10, figs. 7 and 11. 



This unique specimen was found by Mr. Edward Wilson, F.G.S., of Nottingham, on 

 the pit-bank of the Claycross Company's Colliery at Claycross Station, about five miles 

 south of Chesterfield, Derbyshire. Mr. Wilson observes that " this colliery works the 

 Black Shale or Silkstone Seam, the bed of coal which the Geological Survey places at the 

 base of the Middle Coal-measures, dividing that series from the Lower or Gannister 

 series. There can be little doubt that the specimen came from the bind (shaly sand- 

 stone) that forms the roof of that (Silkstone) seam. Therefore its horizon is the base of 

 the Middle Coal-measures." 



This remarkable Cypridinad, though so narrow and compressed, seems to be nearer 

 in its form to Philomedes than to any other of the Cypridi/iada (see pp. 4, S, and 43). 



