Yol. 56.] AND OLDHAMIA. 281 



Associated with 0. antiqua are certain markings which do not 

 seem to have been yet described (PI. XVIII, fig. 9) : these are oval 

 areas, with well-defined slightly raised margins, depressed within 

 like a very obtuse inverted cone, the apex of which is truncated 

 by a circular area of a different texture and colour ; the whole is* 

 the upper end of a corresponding structure that extends vertically 

 downward through the rock (PI. XVIII, fig. 10) ; the central 

 circular area or cylinder is suggestively similar to a worm-tube, 

 and the conical depression with its annular cylinder to the mucilage- 

 cemented wall of such a tube. Whether this structure stands in 

 any direct connexion with Oldhamia antiqua is difficult to determine; 

 the frequent absence of any OZ^Ac^a-appendages around it would 

 suggest a negative answer, but in one case such appendages are to- 

 be seen radiating over the sides of the conical depression and having 

 its apex as their centre ; this, however, is a solitary instance, and 

 may be merely accidental. 



Before proceeding further, it may be at once remarked that, while 

 some of the characters described may be consistent with the theory 

 that Oldhamia is a worm-track, there are several others that ar& 

 difficult to reconcile with such an explanation. The sharply-defined 

 club-shaped processes of 0. radiata are not like any worm-marking y 

 and the relief of the form of 0. antiqua is inconsistent with the 

 nature of a worm-track ; I have endeavoured to meet this objection 

 by suggesting that 0. antiqua represents the excrementitious cast- 

 ings of a worm. It is singular, if this be so, that the two species, 

 0. antiqua and 0. radiata, should be so rarely found together ; 

 some localities, such as Carrick Mountain (Wexford), are said to 

 have afforded abundant specimens of 0. antiqua, but none of 

 0. radiata, and it is a fact familiar to collectors that, though both 

 species occur at Bray Head, they are seldom found in the same bed. 

 We may now pass to the consideration of further features, which 

 are, if anything, still more strongly opposed to the vermiform nature 

 of Oldhamia. 



The rocks in which Oldhamia occurs at Bray are exceedingly 

 fine-grained, highly-laminated, hardened shales, sometimes red, 

 sometimes green. They consist largely, perhaps chiefly, of sericite, 

 with abundant chlorite, granules of ferric hydrate, and sometimes 

 minute grains of quartz. The smooth surfaces of the laminae were 

 admirably adapted to receive and retain the finest impressions, so 

 that the preservation of a trace like Ichnium Wattsii need not cause 

 the least surprise. It is, however, remarkable that no change of 

 colour occurs in the red beds in the vicinity of Oldhamia, but 

 obvious worm-markings are similarly destitute of green borders. 

 Notwithstanding the fineness of grain, there is no reason to suppose 

 that the rocks were very slowly deposited, rather the contrary ; the 

 sandier beds are often extremely false-bedded, and occasional beds 

 of coarse grauwacke are intercalated, as well as numerous massive 

 beds of quartzite. 



In thin slices of the rock devoid of Oldhamia, the laminae present 



