340 MR. E. S. COBBOLD OK THE [vol. lxxvi, 



Dimensions in millimetres. 



Ventral valves [2119]... Length=3\5. Width=3-0. Height = M. 



[ 677]... Length = 2'5. Width = 2-0. Height= ? 



Dorsal valves [2120]... Length=2-8. Width = 2- 6. Height=0-66. 



[ 676]... Length=2-5. Width=2'25. Height^ ? 



Locality and horizon. — Comley, Middle Cambrian ; from the 

 Billingsella Beds, horizon Be. 



Obolus (?) ef. schmalenseei "Walcott. (PL XXII, figs. 22 a 



&22h.) 



Obolus schmalenseei Walcott, 1912, U.S. Geol. Surv. Monozr. vol. li, p. 412 & 



pi. xxx, figs. 19, 19f«-19e. 

 Lingulella (?) spp. pars, Matley, 1911, Q.J. Gr. S. vol. lxvii, p. 301 & pi. xxvi. 



figs. 8 a & 8 b. 



Additional specimens possessing the sub-pentagonal form described 

 by Dr. Matley have come to light since he wrote his notes on 

 the brachiopoda from the Paradoxides Beds of Comley. 



In size and general form they are veiy like 0. schmalenseei, but 

 they lack the fairly strong internal marks shown for that species in 

 Walcott's figures. In the dorsal valve there is a central promi- 

 nence and also two ill-defined concavities under the umbo as in 

 O. gibbosus. 



The specimen figured with Dr. Matley's notes is there called the 

 interior of a brachial valve. From the lateral view there figured 

 it seems more like a ventral. 



The dorsal valve now figured [689] has the length and width 

 equal, the convexity is strong, the test consists of several layers, 

 the exterior is marked by the concentric edges of laminae, and the 

 interior by an ill-defined central ridge extending to a quarter or 

 a third of the length of the shell, with ill-defined hollows on each 

 side under the umbo. 



Length = 3 mm. 



Locality and horizon. — Comley, Middle Cambrian ; from the 

 Billingsella Beds, horizon Be. 



Obolus (?) sp. indet. a. (PL XXIII, fig. 29.) 



A single valve [1604], that is referred to this genus on account 

 of its shape, was found with crushed specimens of Acrotreta and 

 fragments of Hyolithelhis mi cans in fine blue shale, which is 

 mapped as belonging to Horizon Ba 2 . 



Dimensions. — Length = 2 - 2 mm.; width — 2 mm. 



Obolus (?) sp. indet. b. (PL XXIII, fig. 28.) 



A rather large single valve [162 b\ also referred to the genus, 

 was found associated with Acrotreta in sandy shale mapped as 

 belonging to Horizon Bb 2 . 



The specimen is remarkable for its strong convexity and the 

 wide flattened margin of the cast, indicating a thick shell. 



Dimensions. — Lenerth = 3 - 2 mm. ; width = 2"7 mm. 



