The lachrymal occupies a considerable space on the flat surface of the cheek in front of the orbit, and below it the jugal does the same.
In the more extended sense, the Anomaluroidea are diagnosed as follows: In the skull the infra-orbital foramen (or canal) is large, the lachrymal foramen placed high up, and no transverse canal; while the malleus and incus of the internal ear are fused.
Usually only one orifice to the lachrymal canal, situated inside the rim of the orbit.
The portion of the lachrymal duct communicating with the cavity of the nose has, on the other hand, been abnormally developed, apparently for the purpose of cleansing that chamber from particles of sand which may obtain an entrance while the animal is burrowing.
The lachrymal forj amen is always within the orbital margin; and in many species the infra-orbital foramen is very large (in some as large as the orbit) and transmits part of the masseter muscle.
The three remaining families of the Hystricoidea, of which one is African while the other two are chiefly South American, are very closely allied and often brigaded in a single family group. In the Capromyidae, which includes only the South American and West Indian hutias, the South American coypu and the African cane-rats, the tympanic bulla of the skull is hollow, the par-occipital process straight, the lachrymal small, and the cheekteeth rooted, with deep enamel-folds; the first front toe Leing occasionally absent.
A glandular streak extending from the nostril towards the eye is the lachrymal canal.
In the skull there are two orifices to the lachrymal duct, situated on or inside the rim of the orbit.
Vittatus, of Sumatra, characterized by having a broad reddish or whitish band running from the middle of the snout along the upper lip to disappear on the side of the neck; the skull being short and high, with the facial portion of the lachrymal bone small.
In the skull the lachrymal bone is large, the paroccipital process is directed vertically downwards and the tympanic bulla is hollow.