90 Transactions. 



and work. Certain species have been found at as great a depth as 3.000 

 fathoms, though at depths below 1,000 fathoms they are much rarer than 

 at less than 100 fathoms — that is, the great majority live along the con- 

 tinental shelf, and especially along the littoral area." 



This opinion is not conclusive, but it certainly indicates that it is possible 

 for worms to produce borings at the depth at which greensand is deposited. 



The statements of Cayeux (1897, pp. 431-32 and 532-33) are of interest 

 in their bearing on this point. He shows that phosphatic nodules occur 

 in ths chalk of France and Belgium at levels marked by change in the depth 

 of the sea, whether this be in the direction of increasing or of lessening 

 depth — that is, they occur at the points of inflexion of the curves indicat- 

 ing the depths of the sea over the area at any particular time. He says 

 (p. 431), " La production du phosphate de chaux de la base de la craie 

 a Belemnitelles correspond a une rupture d'equilibre de la mer cretacee, 

 phenomene dont on a maintes preuves." These are then given, and among 

 them may be noted the hardening of the upper layer of chalk and the 

 presence of perforations. The first of these is perhaps analogous to the 

 hardening of the fragments in the upper layer of Amuri limestone which 

 may be attributed to phosphatization, and the second is a most character- 

 istic feature of its upper surface. Farther on (p. 432), he says, " La craie 

 phosphatee du department du Nord est en relation avec un mouvement 

 d'exhaussement qui a eu pour resultat de chasser la mer du golfe du Mons. 

 Son existence est liee a une periode de regression de la mer pour le Nord." 

 Of the two instances quoted, the former applies to an increase in depth of 

 the sea and the latter to a diminution in depth. The latter in all probability 

 is analogous to the change from Amuri limestone to calcareous greensand 

 which characterizes the level of phosphatic nodules in the New Zealand area. 



Further, Cayeux considered that the accumulations of phosphatic 

 material took place at such a distance from the shore that the change in 

 depth of the sea did not permit of any marked variation in the character 

 of the terrigenous material associated with the chalk. This is borne out to 

 some extent in the area under consideration, as it has been shown that the 

 material of the phosphate nodules is not markedly different from that of 

 the beds with which they are associated. In any case, Cayeux does not 

 postulate any emergence of the sea-bottom to account for phenomena which 

 are quite analogous to those near the junction of the Amuri and Weka Pass 

 limestones. 



The Peculiarities op the Junction of the Amuri Limestone and 



Weka Pass Stone. 



It must be admitted that the junction of the Amuri and Weka Pass 

 limestones is a peculiar one and demands some special explanation, seeing 

 that unconformity is not admitted. The irregularity of the junction in some 

 places could be attributed to chemical erosion, and the increased amount 

 of phosphate in the detached pieces of Amuri limestone in the nodular band 

 supports this contention ; but it may be explained in another way, or 

 perhaps the two explanations are not mutually exclusive. It seems to us 

 that the so-called erosion surface has been the result of extensive boring 

 during the interval between the deposition of the typical Amuri limestone 

 and the upper more glauconitic part of the bed when it formed part of a 

 sea-bottom. As a result of the complete penetration by borings the upper 

 surface consists in places of peninsulas of limestone surrounded by green- 



