354 ' ME. E. S. COBBOLD OX THE [vol. lxxvi, 



An extreme case, probably an old individual, is now figured. 

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

 Billingsella Beds, horizon Be ; also, sparingly, from horizon Bb.. 



Billixgsella sp. indet. (PL XXIII, figs. 23 «-23 c.) 



A single ventral valve, represented by the external and internal 

 casts [1879, 1880], Avas found in the matrix of the Coniley Breccia- 

 Bed. The specimens do not preserve any of the finer internal 

 markings, and the external characters are but poorly indicated. 

 These consist of some twenty-five angular (?) radiating ribs, 

 which increase at varying distances by interpolation, and are crossed 

 by concentric lines of growth. The ribs are reproduced on the 

 internal surface. 



Dimensions. — Lengths 8 mm. ; width = 9'5 mm. ; height = 

 1*6 mm. 



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

 Comley Breccia-Bed, Paradox kles-intermedius Grits, horizon Bb r 



Oeusia Walcott. 

 Oeusia lenticulabts Wahlenberg. (PL XXIII, figs. 25-27.) 



Orthis (Orusia) cf. lentieularis Wahlenberg, Matley, 1911, Q. J. G. S. vol. Ixvii, 



p. 306 & pi. xxvi. tigs. 24-26. 

 Orusia lentieularis Wahlenberg, Walcott, 1912, U.S. Geol. Surv. Monogr. vol. li, 



p. 765 & pi. xcviii, tigs. 1, 1 a-\ p, 2, 2 a-2 k, 3, 3 a & 3 b, 6, 6 «-6 c. 



Since Dr. Matley wrote his notes additional specimens have been 

 found at Comley, among which almost every variation figured by 

 Dr. Walcott can be matched. There are also internal casts showing 

 the fissures which represent the crural plates of the dorsal valve 

 and the dental plates of the ventral mentioned, 1 but not figured, 

 by Dr. Walcott; the former are comparatively near together and 

 sometimes converge, the latter are wide apart and divergent. 



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

 Orusia Shales, horizon Ca. 



VI. The Comley Pteeopoba, etc. 

 Hyolithus Eichwald. 

 BTroLiTHUs ceassus. sp. nov. (PL XXIV, fig. 28.) 



Type-specimen [2603]. 



Diagnosis. — Shell straight (so far as seen), apparently sub- 

 tmadrate in section, ratio of diameters about 1 to "7, lateral angles 

 well rounded, rate of taper uncertain ; shell-substance of two 

 layers — the inner thick, smooth, and calcareous, the outer thinner 

 and marked with numerous, irregular, and very coarse wrinkles ; 

 aperture transverse on the ventral face, projecting forward on the 

 dorsal, and sinuous at the sides. 



Dimensions. — Apertural diameter, 5 or more millimetres. 

 The length may have been from 1-0 to 50 mm. 



1 1912, p. 767. 



