These holes in a piece of clam shell are left by the Sulphur or Red Boring Sponge.
"Souvenirs from a beach visit on the coast of NJ."
Here's a Neoesperiopsis rigida or Orange Finger Sponge, found growing on a thin line hanging off the dock at the marina. It was about 2" tall at the longest place. Apparently some fish lay their eggs inside these sponges.
Sandy Hook, New Jersey shore in January - some kind of sponge, maybe Halichondria.
This Ophlitaspongia pennata or Velvety Red Sponge was encrusted on the underside of a boulder, visible at low tide. When I examined the photo later, it looks like there may be at least two Red Sponge Nudibranchs living on it.
Here's a beautiful example of Haliclona cinera or Purple Intertidal Sponge, growing on two rocks with barnacles of different sizes.
Here's a 6" square (more or less) patch of Halichondria panicea, called Yellow-green Encrusting Sponge, noticed on a boulder at low tide.
Found at low tide in a sea cave.
Sponges are animals of the phylum Porifera (/pɒˈrɪfərə/; meaning "pore bearer"). They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through them, consisting of jelly-like mesohyl sandwiched between two thin layers of cells. Sponges have unspecialized cells that can transform into other types and which often migrate between the main cell layers and the mesohyl in the process. Sponges do not have nervous, digestive or circulatory systems. Instead, most...