536 5 Transactions. 
Notoaemea, pileopsis up to 28 mm. in length and 14 mm. in height occurs, 
The apexes of all the shells except those of Notoacmea pueosis and young 
ded 
nder stones in this belt are a few molluses, including some not 
able to tolerate drying conditions of exposed rocks. Monodonta lugubris, 
Sypharochiton pellisserpentis, and Atalacmea unguis-almae, all with clean 
uneroded shells, are common. Onchidella is also found here. 
Gasteropod Subformation. 
Perhaps on account of the mobility of its dominant life-forms, this sub- 
formation occurs highest on rocks in the intertidal belt. There are two 
principal growth-forms—gasteropod, with spiral shell, continuous peristome, 
and close-fitting operculum, and associated with this in all situations except 
dry rocks above high-tide mark, where Melaraphe alone reigns, the limpet- 
like growth-form. Several associations may be distinguished. 
This subformation is pro ably represented in all seas. I need onl 
mention the associations of Patella and Littorina on the British coasts, of 
Nerita and Tectarius in the tropics, and of Cellana and Melaraphe in 
Australia. ' 
Cellana- Monodonta Association, 
Otago Harbour.—Rocks between tides at Portobello support a fairly 
typical harbour-community of shelled animals. The substratum consists 
and attain a large size, 
Along the upper limit Melaraphe cincta (18 mm.), with clean non-eroded 
shells, is common. Here are a few patches of Bostrychia arbuscula. Below | 
there follows the main collection, consisting of Monodonta aethiops (alt. 
30 mm.) M. corrosa, Sypharochiton pellisserpentis, Siphonaria zealandica 
‘(25 mm.), S. obliquata (young), Cellana ornata, Risellopsis varia (diam. 8 mm.), 
Patelloidea stella corticata, and, on the larger shells, Notoacmea daedala. 
under stones occur Amaurochiton glaucus (always of a dark-green colour). 
Notoacmea pileopsis, and М. daedala. 
Cellana-Melaraphe Association. 
Shag Point.—Of the associations included under the gasteropod sub- 
formation the present is the richest that I have examined, both in number 
_ of species and in individuals. The size of the shells, too, is in most cases 
