Marshall. — Tlie Yoiinr/cr Lltiiesfones of Xeir Zealand. 91 



DESCRIPTIONS OF LIMESTONES FROM THE LOCALITIES NAMED ABOVE. 



A. PoLYzuAL Limestones. 

 (rt.) Waiomio Limestone, near Kawakawa, Bay of Idaiids. Plate VIII, fig. 1. 



Foraminifera of relatively large size frequent : TnmcatuUna, Nodosaria, 

 a thick-walled Carpenteria, Glohigerina, and a moderate-sized nearly round 

 form of Amphistegina. Spines and plates of echinoderms in a perfect state 

 of preservation are very frequent. Polyzoa are abundant. There is much 

 glauconite in separate rounded grains. Occasional small grains of fine 

 sandstone. Mr. F. Chapman, of Melbourne, writes, " The Waiomio lime- 

 stone is of the typical Miocene character." 



(6.) Horahora, Whangarei. Plate IX, fig. 2. 



VeiT similar to the rock from Waiomio, but it contains much less 

 glauconite. Polyzoa are somewhat more abundant at the expense of the 

 Foraminijera. In particular, Glohigerina and Carpe'nteria are not in my 

 sections, but Amphistegina is rather more abundant. 



(f.) Waro, near Whangarei. 



Echinoderm fragments are very plentiful, and, with Polyzoa, constitute 

 nearly the whole material of the rock. There are occasional Foraminifera, 

 including Amphistegina and Rotalia. Some secondary calcite has crystal- 

 lized round the echinoderm fragments. A little glauconite is present, but 

 there are no grains of foreign rock matter. The subcrystalline nature 

 often mentioned in this and similar limestones is entirely due to the frequent 

 occmTence of plates and fragments of echinoderms. 



{d.) Gibraltar Rocks, Pahi Arm, Kaipara Harbour. 



A coarse-grained type, mainly composed of Polyzoa. Echinoderm spines 

 and plates are large and perfect, with a little secondary calcite in the inter- 

 stices. Foraminifera are not numerous, but Carpenteria, Glohigerina, and 

 Rotalia occur, and the small round Amphistegina is fairly common. No 

 Lithothamnium can be seen. A little glauconite, but no grains of foreign 

 rock matter. Mr. Chapman says, " The Amphisteginae of this rock are of 

 a varietal form denoting rather deep water." 



(e.) Limestone Band in Greensand, Pahi, North Auckland. 



Polyzoa and echinoderm fragments are here of less importance, and 

 Foraminifera and Lithothamnium are in considerable quantity. Of the Fora- 

 minifera, Spiroplecta, Truncatulina, and Glohigerina are the most common ; 

 but there are many individuals of a smaller type of Amphistegina than in 

 the preceding rocks. Very little quartz, but a considerable quantity of 

 glauconite. 



(/.) Wiwiku Island, Kawhia Harbour. 



In hand-specimens a coarse-grained type. In section reijiains of Polyzoa 

 and echinoderms are seen to form the greater part of the material. Amphi- 

 stegina, apparently the same species as at Waiomio and Horahora, is quite 

 plentiful. Angular quartz grains are quite frequent. Several specimens 

 of Rotalia calcar in the section. The ordinary limestone of the mainland 

 varies considerably in different horizons. Amphistegina occurs in a band 

 100 ft. above the base. 



