HERPETOLOGY, her-0461'61i, the study of reptiles. In its earlier days, included under the term °reptile° were not only those now properly so named, but also the amphibia (q.v.) and some other °creeping things" not in either group. Cuvier's classification, the first approach to a scientific one, put both the true reptiles and the amphibians as corciated groups under Reptilia; but their distinction in form was soon perceived. Huxley showed that in their descent, embryology and structural rela tions, the amphibians were more closely re lated to the fishes than to the reptiles (lizards, serpents and turtles). He therefore united the two in a superior group lehthyopsida, while he joined the birds to the reptiles in a group of similar rank called Sauropsida. But more recently the limits of herpetology have been restricted to truly scientific limits— the chor date class Reptilia, a definite group distinguished by the following characters: Reptiles are cold-blooded, the temperature of the body not differing much from that of the natural surroundings, and rising or falling accordingly; the heart is three-chambered, ex cept in crocodilians, where four chambers first occur in the upward scale of natural creation; mostly venous blood goes from the heart to the anterior viscera, and mixed blood to the posterior region, only the head and anterior regions receiving pure arterial blood; through out their whole life they breathe with lungs, never with gills; the body is covered with scales, with which subjacent bony plates or scutes are sometimes associated i the vertebra are absolutely gastro-centrous (biconcave) ; the skull articulates by a single condyle with the backbone, and the lower jaw works against the quadrate bone; the great majority are ovip arous, while in some the eggs hatch within the mother.
This characterization unites into the one class one order represented by a single living species (the eTuatera Lizard”, and the exist ing tortoises and turtles, lizards, snakes and crocodiles and many others now extinct. The group occupies a central position in. the verte brate series. Above it on the scale of organiza tion are the birds and mammals; below it the amphibians and fishes. In respect to their phy
logeny Gadow is authority for the statement,
the other hand, there is not the slightest doubt that they are evolved from some branch of the Stegocephali (q.v.), whilst on the other hand the reptiles, probably through some branch of the Theromorpha, have given rise to the mammals; some other reptilian branch, at pres ent unknown, blossomed out into
The uncertainty arising from the more or less fragmentary testimony of the fossil re mains of reptiles of geologic times has neces sarily a restraining effect upon the completion of a classification of the reptiles. Moreover, the distortion of skeletons in the processes of fossilizing renders close decisions as to genera and species very difficult. It is cus tomary, therefore, with cautious scientists to halt the differentiation downward at the sub order, recognizing that in the present state of knowledge of the Reptilia all classification must be tentative. The most recently attempted classifi cation is that of Dr. Samuel Wendell Williston, presented in 1914, and this may be said to be the most that can be done with the data now available. Dr. Williston divides the class Reptilia into 12 orders and three provisional orders, as follows: Cotylosauria, with five sub orders; Chelonia, with three sub-orders; Thero morpha, with three sub-orders; Therapsida, with three sub-orders; Sauropterygia, with two sub-orders; Proganosauria (provisional) ; Ichthyosauria; Protorosauria (provisional) ; Squamata, with three sub-orders; Thalattasauria (provisional) ; Rhyncocephalia, with three sub orders; Parasuchia, with three sub-orders; Crocodilia, with two sub-orders; Dinosauria, with three sub-orders; Pterosauria, with two sub-orders. The anatomical differences upon which these divisions are established are de tailed in Dr. Williston's