Pachymatisma johnstonia

Pachymatisma johnstonia is a species of sponge belonging to the family Geodiidae. A species of the north-eastern Atlantic coasts, this is a usually grey encrusting sponge with large prominent oscula and a pale yellow interior. The size and form depends largely on the extent of its exposure to waves. In heavily wave-exposed locations, it is usually small and thin but in more sheltered places can grow to over 50 cm across and 15 cm thick.

Pachymatisma johnstonia
Scientific classification
Kingdom:	Animalia
Phylum:	Porifera
Class:	Demospongiae
Order:	Tetractinellida
Family:	Geodiidae
Genus:	Pachymatisma
Species:	P. johnstonia
Binomial name
Pachymatisma johnstonia Bowerbank in Johnston, 1842
Synonyms
Caminus osculosus Grübe, 1872 Halichondria johnstonia Bowerbank in Johnston, 1842

References

• Pachymatisma johnstonia at World Register of Marine Species
• Barratt, John H.; Yonge, C. M. (1958). Collins Pocket Guide to the Sea Shore. William Collins, Sons. p. 43.