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House Guests

Updated: Feb 12, 2020

'House Guests' was an exhibition at Kettle's Yard which saw artefacts from several Cambridge museums seamlessly incorporated into the regular collection. The below text and accompanying interview with Dr Kenneth McNamara, director of the Sedgwick Museum of Earth Sciences, appeared in the exhibition catalogue.

Ammonite, Australiceras Gigas

In a quiet corner of Kettle’s Yard, away from the flooding sunlight, the great hooked ammonite sits. A weighty thing. It is perhaps a foot across. In form it starts with the tight formality of a tidy swirl before stretching out like a barbarous tusk, its surface erupting into ridges and troughs, a mountain range. For the final part of its journey it curves back on itself, almost a question mark, and stops abruptly. It is the shape of a doodle in the corner of a page, both familiar and suddenly altered.

Spirals are warm, satisfying forms. They seem essentially pure and complete. The proportions of an ammonite’s spiraling shell obey the divine section, a ratio said to describe the proportions of perfect beauty with a mathematical formula. In this species, Australiceras, mathematical perfection is abandoned. It’s a change we recognise intuitively. It echos a shift in focus in much of the art Jim Ede collected as it moved away from Euclidean geometry towards more complex and irregular forms. On a low table in his bedroom Jim carefully arranged pebbles in a spiral. He selected stones that were perfect spheres worn smooth by currents and placed them on warm wood in a puddle of sunlight next to a jagged counterpoint, a diminutive bronze by Henri Gaudier-Brzeska. Our ammonite seems to echo this pairing on its own, the clean simplicity of a spiral disrupted by that pagan outcrop. It is in fact only an ancient impression, the heavy shadow of a creature long dead, its kind extinct. Because the fleshy parts of ammonites are never found preserved it is also incomplete and inscrutable.

Its closest living relative, the nautilus, is found in the depths of the ocean. It lives in the dark, its eyesight poor, but is patterned in painterly stripes, lobster bisque on opal. In video footage it gleams aqua-white and jewel-like in a shaft of light from a diver’s torch and bobs strangely. Buoyant and propelled by water jets, its gentle movements seem foreign. Translucent tentacles taste the sea to help it find its way.

In shape and lightness and sense of fragile balance it reminds me of Naum Gabo’s Construction in Space: Suspended (1962) which usually sits in the extension of the House, currently closed for renovations. Far from the familiar completeness of wholesome symmetry this petite sculpture’s curious beauty is drawn from the taut relationship between delicately balanced asymmetric forms and the space caught between them. It’s unfamiliar shape invites exploration. Strange and intangible it shivers with ambiguity like a living thing. I picture the sculpture, golden arc and opaque form, packed away from light and curious gaze. The nautilus descends, fading into the gloom. The last clue to a creature once buoyed by ocean currents that spanned half the world. Particles of sediment glint in the narrow beam of torchlight, the dark sea all around, we conjure Australiceras in its place. A ghost, its body almost completes the strange loop of its shell. It would have been the shape of a zero, empty in the centre. With its spiral held aloft it is precarious, its balance delicately, curiously negotiated.

In Kettle’s Yard the ammonite rests, lumpen, sturdy counterweight to its imagined self. A solid mass to anchor luminous imaginings.

Interview with

Dr Kenneth McNamara

Director of the Sedgwick Museum of Earth Sciences (who selected the fossilised ammonite for display at Kettles Yard).

Cecily McNamara: What can you tell me about the object you have chosen?

Dr Kenneth McNamara: The specimen is a fossilised ammonite. These are an extinct group of cephalopods (that’s the group that today includes octopus, squid, nautilus etc.) Like the modern nautilus, ammonites had a squid-like body that lived within a (usually) coiled shell. The nautilus has exactly the same body plan. The inner part is a chamber demarcated by a little wall and filled with gas and a little liquid. It had the ability to change the gas pressure inside, this is the assumption based on what the nautilus does, which enabled it to move up and down in the ocean through hundreds of meters.

CM: Why did you choose this one in particular?

KM: Such large ammonites as this type are not very common. They are also rather unusual in the generally ammonites formed a spiral shell, but in a group known as ‘heteromorph’ ammonites, the shell can be partially or completely uncoiled. In an Australiceras like this one, the shell started coiling as in a ‘normal’ ammonite, it then uncoiled to produce a straight shaft, then coiled again to form a large hook-like outer part of the shell. We have no idea why it did this. The reason these were coiled in the first place, (because their early ancestors were straight), is that it makes the shell a very stable orientation and shape, with the animal at the bottom and the shell coiled above. The uncoiling we see here inherently makes the ammonite very unstable and it loses its simple symmetry. I think this means it would have had a very different mode of life from ‘normal’ ammonites, which are thought to have been free swimmers. Hereromorph ammonites, though, may have crawled around on the ocean floor.

The other bit of the story, I suppose, is that you can see the old labels on this specimen. They reflect the different people who have studied it at different times. If it has been figured in a particular scientific paper the little blue label will actually say. So as well as the history of the object, its intrinsic history, there is the history of what people have done with the specimen in terms of studying it.

CM: Where is it from?

KM: This specimen was collected by Reverend Thomas Wiltshire, probably in the mid-nineteenth century, from Atherfield, which is on the southern coast of the Isle of Wight. It’s about 130 million years old.

CM: Why is it special to you?

KM: I am fascinated by these particular shells because many years ago, when I first went to Australia in the late 1970s, I went fossil collecting in Queensland. I was looking for this type of ammonite but was decidedly unsuccessful. When I stopped at one station’s homestead to ask the owner’s permission to look for fossils on their land, they suggested I look through the rockery in their garden. This I did, and I found a large rock with a tiny bit of ammonite sticking out. They allowed me to take the whole boulder once I had found a replacement. I took it back to my lab in Brisbane and after eight hours of careful preparation with a small hammer and chisel, a complete ammonite, much like this one, appeared. It also turned out to be a new species, which was exciting.

The other thing that intrigues me is in its name. It is called Australiceras because this type of ammonite was first found in Queensland, in the same rocks where I was looking. So we have much the same species occurring in the Isle of Wight as in Queensland, 130 million years ago. This is further evidence that these two regions were connected by the huge sea called Tethys, the precursor of the present day Indian Ocean and Mediterranean. But if they were just crawling around on the sediment surface it makes you wonder just how they spread so far and wide from Australia to the Isle of Wight. It may be that in their early life they were coiled or that when they were larvae they got caught in ocean currents and could have been transported large distances. I think they must have had a change in their life and went from being these active swimmers to probably becoming much more sedentary. I think it’s a fascinating story, but there is a lot we don’t know.

CM: What would they have looked like?

KM: You find some ammonites with the mother-of-pearl of the shell preserved on them that would have been on the inside like abalone. On the outside they probably had colour on some of them. Imagine the modern nautilus which have nice brown and white patterns. We don’t know the actual colours but I am sure they would have had some patternation because it helps, for camouflage, if you have different colours just breaking up your shape. This was originally quite a delicate shell that’s been turned into this great concrete like object.

CM: Have you thought about how this will sit in a space like Kettle’s Yard?

'House Guests' was an exhibition at Kettle's Yard which saw artifacts from several Cambridge museums seamlessly incorporated into the regular collection. The below text and accompanying interview with Dr Kenneth McNamara, director of the Sedgwick Museum of Earth Sciences, appeared in the exhibition catalogue.


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