118 TEANSATIONS OF THE [FeB. 23 



The other clei^osits of phosphates kuown to me do not show 

 very close analogies to ours, or are similar in their occurrence 

 to those above mentioned. 



Origin. — The origin of the Hauford Brook nodules cannot be 

 considered as decided by this investigation ; but some con- 

 sideration may be noted, bearing on what seem to be the most 

 probable methods of formation. 



The only one that has as yet been suggested for them is that 

 they ma}' be coprolites. In this case ttiey must be referred to 

 some animal much larger than any known from this formation ; 

 the animal might, however, as has been suggested by G. F. 

 Matthew, have been soft-bodied, and hence not preserved, and 

 there are indirect evidences of the existence in the Cambrian 

 seas of some large soft-bodied animal probably related to the 

 squids. But the trilobites found in the nodules are only 

 occasionally comminuted ; generally they are complete heads ; 

 occasionally complete bodies. In Zone 2 especially, but to some 

 extent also in Zone 3, there is usually a nucleus which is 

 sometimes a single trilobite test, sometimes two or three, or a 

 number of fragments. The material collects rather on the 

 inner side of the test than on the outer. Were the nodules 

 coprolites, one would expect to find the tests thoroughly 

 comminuted, and evenly distributed throughout the mass. 



Another view, applicable especially to those of Zone 2, would 

 consider them as fossil sponges which, like those of the English 

 Greensands, have had their organic matter replaced ^by 

 .phospate of lime or iron. The occurrence of spicules 

 and gemmules, the regulfir shape and uniform size, and 

 the frequent presence of a central part of different tinge from 

 the rest, indicating perhaps a cuj^-shaped or hollow centre' 

 favor this view. The darker rim of the nodule is similar to 

 that observed in those of the English deposits. The compara- 

 tive scarcity of Si^icules and absence of any trace of canals, 

 might be exi^lained by considering the sponge to have had 

 keratose or calcareous spicules, and to have been much decom- 

 posed and shrunken before phosphatization. Or there may 

 never have been any canals, but only the central opening. The 

 presence of the foraminifera and other foreign bodies might 

 be explained b}' supposing them to have drifted into the openings 

 after the death of the sponge. But the trilobites are not so 

 easily accounted for, as they often traverse the nodules from 

 side to side in a way that would seem inconsistent with the view 

 of the latter being fossilized sponges, And they are not cup- 

 shaped, as far as can be seen by the eye, but regularly round 



