Yol. 6^.~] ON" FULLERS'-EATLTH BKACHIOPODA. 431 



equal parts, each containing about ten strong ribs, which are 

 lengthened and depressed on one side of the anterior margin. The 

 beak is long, acute, and pointed, recurved at the extremity, but 

 is separated by a foramen from the umbo of the dorsal valve. The 

 beak-ridges are sharp and well-defined. The dorsal valve is slightly 

 compressed near its umbo, and is also twisted — half of the ribs 

 being lengthened to meet the shorter ribs of the larger valve. The 

 anterior margin of the shell is gradually elevated on one side to the 

 middle of the shell, then sharply depressed, and again gradually 

 elevated to the edge of the shell. 



Rhynchonella plateia, 1 sp. nov. (PI. XXVIII, figs. 8 a-S c.) 



T.l. Farmcoinbe Quarry, near Doulting (Somerset). 

 H. Fullers' Earth (Knorri-C\ays) . 



V- 



Colin. L. Kicliardson. 



Diagnosis. — Shell equilateral, its length being nearly equal to 

 its width, and ornamented by well-developed ribs. The ventral 

 valve is slightly convex, curving towards the beak, and depressed in 

 the middle, forming a wide central fold, which is compressed towards 

 the anterior margin. The beak is prominent, curved at its extremity, 

 and separated from the dorsal valve by a rounded foramen with 

 deltidial plates below. The beak-ridges are well-defined. The 

 dorsal valve is nearly flat, but slopes sharply towards its umbo, 

 giving it an equilateral form ; it is ornamented with strong ribs, 

 which radiate from the umbo. The anterior margin has a wide com- 

 pressed fold. 



Remarks. — This shell is remarkable for the flatness of the 

 smaller valve and for its equilateral shape : hence the specific name. 



Rhynchonella Smithi, Walker. 



1877. Walker in Davidson, ' Monogr. Brit. Foss. Brach.' Suppl. (Palseont, Soc.) 

 vol. iv,.p. 213 & pi. xxviii, tigs. 1-3. 



This shell is very characteristic of the Fullers' Earth. The 

 Rhynclionella varians of Schlotheim is a collective species. The term 

 ' varians' might be used as a subgeneric name. 



Rhynclionella Smithi has been found at Chesterblade, Whatley, 

 Oldford, and Midford, but not in the immediate neighbourhood of 

 Doulting — for example, at the Doulting-Bridge or Farmcombe 

 Quarries. 



Rhynchonella Walkeei, Richardson, 2 sp. nov. (PI. XXVIII, 

 figs. 6 a-Q d.) 



T.l. Wellow, near Radstock. 

 S. Fullers'-Eartn Rock. 

 r\. suhcontracti. 

 Colin, diaries Upton. 



Greek, irkaru^, -eta, -v, Hat. 



2 Before Mr. Upton sent me this specimen I had to mourn the loss of my 

 colleague. I dedicate this species to Mr. J. F. Walker, as a slight recognition 

 of the services that he has rendered to students of the Brachiopoda. 



Q. J. G. S. No. 252. 2 i 



