part 4] CAMBRIAN HORIZONS OF COMLET. 339 



a circle ; the front is broadly rounded, the slopes forming- the beak seem to be 

 nearly straight, and make a somewhat obtuse angle. The surface is not well 

 preserved in any specimen ; judging-, however, from some small fragments, I 

 should think that a concentric striation is prevailing, but there are also 

 radiating ribs. In the inner shell-layers little more than longitudinal striation 

 is seen : the innermost are perforated by small punctiform pits. The inner 

 layers are polished and glossy, the outermost seems to. be opaque.' 



Except that the Shropshire specimens do not reveal the puncti- 

 form pits on the innermost layer and that the radiating ribs are 

 not seen, the above description exactly applies to the two Comley 

 shells, both of which were found associated with Billing sella 

 lindstroemi and Acrotliele coriacea ; Linnarssoh's specimens were 

 obtained from ' loose masses ' of bituminous limestone belonging to 

 the strata with Paradoxides forchammeri, and associated with the 

 same two species and also ' Orthis exporrecta.'' For some reason 

 that is not explained, Dr. Walcott l refers these blocks to the 

 Paradoxides-celandicus Zone. 



Neither of the two Comley specimens exhibits the interior sur- 

 face, and only a very small portion of the exterior is seen in one of 

 them (see fig. 23 a). This is near the umbo, and shows concentric 

 striatums, but no trace of radiating ribs. In both specimens the 

 shell is thick, and consists of several layers. In one of them 

 are two raised bands (see fig. 23 b) on one of the inner layers 

 diverging at an acute angle from the apex, recalling the ' flanges ' 

 noted by Dr. Matley 3 in a fragmentary specimen that he referred 

 with some hesitation to Lingulella. A minute shell (fig. 25) 

 possibly represents a young form of the species. 



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

 Billincjsella Beds, horizon Be. 



Obolus (?) gubbostts, sp. nov. (PI. XXII, figs. 20 & 21.) 



Type-specimen [2119]. 



Diagnosis. — Ventral valve : outline a wide oval, from which the 

 apex extends well back beyond the posterior margin, so that the 

 shell is somewhat pear-shaped ; convexity very strong and fairly 

 even in curvature, apex curved down to a height above the mar- 

 ginal plane of the valve that is less than half the maximum height 

 of the valve ; area more or less concave, inclined at an angle of 

 about 45° ; shell thick, marked by a few raised radiating lines, 

 crossed by concentric bands of varying depths of colour, and also 

 by the ragged edges of successive layers of shell-material. 



Interior without marks, so far as known from internal casts. 



Dorsal valve : outline oval, narrowing slightly posteriorly, 

 strongly convex, curvature flattening a little anteriorly ; surface 

 marked by several ragged edges of shell-material ; interior with a 

 slight oval prominence under the umbo, on either side of which lie 

 two ill-defined concavities ; otherwise devoid of vascular marks. 



1 1912, p. 424. 



- 1911, p. 301 & pi. xxvi, fig. 7. 



