OLIVER. Marine Littoral Plant and Animal Communities. 541 
small, with high concentric ribs, and with the posterior end often eroded, 
stained, or attacked by a borer. Tellina liliana occurs in fewer numbers. 
Scattered thickly over the surface of the mud are Cerithidea bicarinata 
and Cominella lurida. The latter animal is carnivorous, and is often found 
congregated in large numbers round its prey. counted forty - two 
crenata is abundant. The shells of the species, though often stained, are 
very successful in ‘resisting erosion. The rotoconch may frequently be 
Antigona shells; Crepidula crepidula, on Turbo smaragdus ; small Amauro- 
chiton glaucus, Elminius modestus, and Notoacmea parviconoidea, on Turbo 
and Amphibola. : 
Parenga Harbour. — Mud-flats between tides where not covered by 
Zostera are occupied below the surface by crabs, Helice crassa, and a few 
Antigona stutchburyi. The shells of this species here measure as much as 
40 mm. in length, whilst in the adjacent Zostera beds the usual size is about 
half this. On the surface in this association are Amphibola crenata, Ceri- 
thidea bicarinata and Cominella lurida. Shells of Cerithidea bicarinata attain 
a length of 33mm.; the largest shell gathered on the Zostera beds was 
22 mm. long. i 
Heathcote Estuary —Mud-flats without Zostera or algae occupy the 
greater portion of the Heathcote Estuary. Everywhere are crabs’ burrows 
occupied by Helice crassa and Heterograpsus crenulatus. Just beneath the 
surface of the mud is Antigona stutchburyi, while deeper, about 10 cm. from 
the surface, is found, but less commonly, the larger pelecypod Mactra ovata. 
Everywhere down to a depth of 10 cm. to ; 
pies cylindrica and dees papillosa. Оп the surface Amphibola crenata 
i M nta corrosa and Cominella lurida, 
all three species having the shells considerably eroded. | On the larger ` 
ot pileopsis. 
‘along the edge of the mud-flats are burrowed into by Helice crassa ; under 
stones on the flat are Heterograpsus crenulatua, Melita inaequis, and the 
worms Nereis kerguelenensis, Nephthys macrura, and Scolecolepides benhami. 
(Plate 49, fig. 2, Lyttelton Harbour.) 
Phytia Association. 
cks near high-water mark on the south coast of 
Rangotito there is a good deal of mud, and here is developed an association 
perhaps related to the mud-flat посао HE M, pe ау аз е“ 
ni iati n rocks are related. e animals are toleran 
Miu pen por dear half their time out of water. Two of 
re pulmonates. Phytia ornata 1s the 
t nd i on mud in shady places and under 
stones; Marinula filholi is not so common. Other members of this 
iation, which comprises only smal Cies, 
po ed pin NM algae and under stones, and Potamopyrgus 
