The Sheep's Ear Abalone, Haliotis ovina, has a dorso-ventrally flattened, oval-shaped shell compared to most other gastropods such as land snails or trochus shells. It has a distinctive flattened spiral feature (the spire) at the posterior end of the dorsal surface of the shell. A number of holes (tremata) along the left edge of the shell are also indicative of the Family Haliotididae, but there is a large amount of variation with respect to the number, size and elevation of these holes and they should be used with caution in conjunction with other features to identify species within the Family (Jarayabhand and Paphavasit, 1996; Geiger and Groves, 1999; Geiger and Poppe, 2000). Some of these tremata close over during growth and development and there is such variation that this should not be used diagnostically.

Diagram modified from Geiger and Poppe, 2000.

On the ventral surface of the shell, a nacreous flattened area (the columella) is present (Geiger, 1998; Geiger and Poppe, 2000). Nacre is the shiny inner layer of the shell, made of the aragonite form of calcium carbonate and is also known as 'mother of pearl' (Cusack et al., 2013; Geiger and Poppe, 2000).

H. ovina has a strong muscular foot, with a fleshy girdle, called the epipodium (pictured top left) which can be visible in situ, as well as two anterior tentacles which can be periodically extended (Geiger and Poppe, 2000; Ruppert et al., 2004), but more frequently the animal is contained within the shell. These features are covered in the 'Anatomy and Physiology' section of this web page.


 
The following description of H. ovina is in comparison to other members of the genus Haliotis:-

Shell - medium sized (to 92 mm)
Weight - medium to heavy
Spire - visible in ventral view (after animal removed from shell)
Tremata - between 3 and 5 open
- medium to large size and round in shape
- strongly elevated with respect to shell surface
Nacre - brilliant white
Muscle scar - not visible

The majority of the other descriptive features of the shell are highly variable. Colour can range from green to red and have striking spiral patterning or subtle transitions (like a water colour painting) or can even be blotchy in appearance.

H. ovina can be distinguished from the other two tropical abalone species. H. asinina has a longitudinally elongated shell compared to the others and H. ovina is rounder and has more elevated tremata with a more distinct ledge between the columella and the row of tremata than H. varia (Geiger and Poppe, 2000).