198 W. H. Hudleston — Creechharroiv in Purheck. 



in outline, thus causing an appearance of being open at one end, like 

 a horseshoe. Specimens subsequently obtained showed that this 

 was not exactly the case. Where the periphery of the section is 

 complete, as in the specimen figured on Plate XI, Figs. 2 and 3, 

 it is seen that the section of this large concretionary body is thick at 

 one end and thin at the other. Fig. 3 of the Plate especially 

 shows a side view of this curious body, where, taken by itself alone, 

 it might almost be regarded as a fragment of a big belemnite. The 

 section shows a series of concentric rings of brown calcite with 

 a large hollow in the centre filled with the ordinary matrix. There 

 is no radial structure ; one end of the circle, as previously noted, is 

 thick, whilst the opposite end thins out to such an extent that 

 in some specimens it is not to be traced. Some of these ' horse- 

 shoe ' sections are nearly 1^ inches in diameter. 



The Egg-like Body. (Plate XT, Fig. 4.) — For a long time these 

 so-called horseshoe concretions were a puzzle to me, and as they 

 were for the most part only obtained in fragments, there seemed to 

 be no possibility of solving the enigma. At last, by good luck w© 

 stumbled on a still more curious body, which is perhaps the most 

 perfect pisolite ever discovered. In this case we perceive a pisolitic 

 concretion with an interior like a very small egg, of which the 

 shell, represented by the concentric layers of brown calcite, i& 

 developed so obliquely that it is quite thick on one side and thin on 

 the other side. This specimen has been broken so fortunately that 

 we recognize our horseshoe section at once, with the matrix in 

 the form of an egg projecting from the unequally developed circle. 



Those who regard pisolites as organic will doubtless welcome 

 this egg-like form as a new species. But, as a further illustration of 

 the eccentricities of concretionary action, I would direct attention to 

 Fig. 1 of Plate XI, where the shell of a univalve, most probably 

 a MeJanopsis, has been encysted in a number of concentric layers of 

 brown calcite. A similar concretionary action has taken place 

 round other specimens of univalve shells, of which sections are given 

 in Figs. 6 and 8 of the same Plate. This action is interesting from 

 a lithological point of view, but, as we shall perceive subsequently, 

 it renders the palseontology more difficult of interpretation. 

 However, the above instances serve to show that concretionary 

 action has been rampant in the Creechbarrow Limestone, and it is to 

 this action that we must ascribe most of the peculiarities of the rock. 



In those cases where the pisolitic concretions are numerous and 

 the limestone is very compact, as shown in Fig. 4, the rock 

 cuts well and takes a fairly good polish. In this instance the 

 ground-mass is of a dull cream colour, mottled with buff patches, 

 and the sections of the pisolites appear in dark brown calcite, which 

 contrasts well with the non-crystallized matrix. There is much 

 more variety in the shapes of the pisolites than can be gathered from 

 the small fragment figured, but they may be classed as quadrate, 

 circular, and oblong, some showing considerable irregularity of 

 outline. Whatever may be the shape of these smaller concretionary 

 bodies, they conform to the conditions already detailed with regard 



