The deviation from the normal type is much greater still when we consider the degraded, worm-like members of the families Typhlopidæ (Fig. 4, p. 43) and Glauconiidæ (Fig. 5), in which the skull is very compact and the maxillary much reduced. In the former this bone is loosely attached to the lower aspect of the cranium; in the latter it borders the mouth, and is suturally joined to the premaxillary and the prefrontal. In both the tranverse bone and the supratemporal are absent, but the coronoid element is present in the mandible. [Illustration: FIG. 6--SKULL OF _Tropidonotus natrix_. (From British Museum Catalogue of Snakes) Lettering of the bones as in Fig. 3] The principal modifications of the skull in the European genera may be contrasted as in the following synopsis: I. Quadrate articulating with the cranium, supratemporal absent; mandible much shorter than the skull, with coronoid bone; maxillary small, on lower aspect of cranium; pterygoids not extending to quadrate; nasals forming long sutures with the premaxillary, prefrontals, and frontal _Typhlops._ II. Quadrate suspended from the supratemporal; mandible at least as long as the skull; pterygoids extending to quadrate or mandible. _A._ Mandible with coronoid bone; nasals in sutural contact with frontals and prefrontals; transverse bone short, not projecting much beyond cranium; maxillary not half as long as mandible, which is not longer than skull (to occiput) _Eryx._ [Illustration: FIG. 7--SKULL OF _Zamenis gemonensis_. (From British Museum Catalogue of Snakes)] _B._ No coronoid bone; nasals isolated. 1. Maxillary elongate, not movable vertically. _a._ Maxillary half as long as mandible. Supratemporal half as long as skull, projecting far beyond cranium; mandible much longer than skull _Tropidonotus._ Supratemporal not half as long as skull, projecting far beyond cranium; mandible much longer than skull _Zamenis._ [Illustration: FIG. 8--SKULL OF _Coluber longissimus_. (From British Museum Catalogue of Snakes)] Supratemporal not half as long as skull, projecting but slightly beyond cranium; mandible much longer than skull _Coluber._ Supratemporal not half as long as skull, not projecting beyond cranium; mandible not longer than skull _Coronella_, _Contia_. _b._ Maxillary not half as long as mandible, which is longer than skull; supratemporal not half as long as skull, projecting beyond cranium. [Illustration: FIG. 9--SKULL OF _Coronella austriaca_. (From British Museum Catalogue of Snakes)]