Cope (Proc. Ac. Philad., 1864, p. 230) resorted to the modifications of the squamosal, ectoand endopterygoid bones, the condition of the vestigial limbs, and the teeth:- Scolecophidia (Typhlopidae), Catodonta (Glauconiidae), Tortricina (Ilysiidae and' Uropeltidae), Asinea, Proteroglypha and Solenoglypha.
Ilysiidae Xenopeltidae Colubridae Aglypha Typhlopidae Boidae Glauconiidae 'This means that the Boidae retain most primitive characters.
Likewise primitive, but in various respects degraded, mainly owing to burrowing habits, are the Typhlopidae with the Ilysiidae, and Uropeltidae as a terminal branch, and on the other hand the Glauconiidae.
- Burrowing like the Typhlopidae, which they much resemble externally, but the maxillaries retain their normal position and are toothless, teeth being restricted to the lower jaw, which is short, stout, and not distensible.
They are viviparous like the Typhlopidae, upon which they feed besides worms and insects.