16
THE ESSEX NATURALIST
Order Perithcha
VORTICELLIDAE
Some unidentified occurring with the last mentioned.
Phylum PORIFERA
Class CALCAREA
HOMOCOELIDAE
Leucosolenia complicata (Montagu)
Common on clean shelly bottoms, mainly attached to hydroids
and weeds. Thirslet Creek.
Sycon ciliatum (Fabricius)
Common on the bottom along the north shore of the Black-
water from Thirslet to Mill Creek (1960) and also at other places.
Density of 195 per nr recorded from station TL.l (11.5.1960).
Grantiidae
Grantia compressa (Fabricius) Purse Sponge
Recorded from the bottom at stations TL.l, TL.2, Cl and
S.14 in 1960. Occasional.
Class DESMOSPONGIARIA
Order Tetractinomorpha
OSCARELLIDAE
Oscarella sp.
Doubtful record; Bradwell Creek, 1960.
Clavulidae
Cliona celata Grant
Common; boring into dead shells of oysters and other mol-
luscs and widely distributed over the bottom. Recorded from
stations S.2, TL.2, N.1, S.3, S.4, S.5, S.6, C.1, N.2 and S.21 during
1960.
Order Ceratinomorpha
Haploscleridae
Haliclona oculata (Pallas)
Common on bottoms of shell and shell with mud. Recorded at
stations S.3, S.7, C.3, HB.3, and HB.4 in 1960.
Desmacidonidae
Halichondria panicea (Pallas) Bread Crumb Sponge
Very common as branched, encrusting masses on clean shell
and shingle bottoms. Widely distributed seawards of Osea Island
but found particularly on shingle at stations TL.2 and TL.3 and
down the middle of the Blackwater.