Long, from snout to end of tail, the exserted portion of the tusk may measure 6 or 7 and occasionally 8 ft.
It is often exserted with a rapid motion, sometimes with the object of feeling some object, sometimes under the influence of anger or fear.
The tongue is short, and the sheath in which it lies concealed opens near to the front margin of the lower jaw; scarcely more than the two terminating points are exserted from the mouth when the animal is in the water.
They are succeeded by succulent fruits, which are exserted, and frequently scaly or spiny, in which respects this genus differs both from Melocactus and Mammillaria, which have the fruits immersed and smooth.
The four succeeding sections, in which the ovipositor is modified into a sting (always exserted from the tip of the abdomen) and the trochanters are with few exceptions simple, form the Aculeata of Linnaeus.