THE CLASSIFICATION OF SNAKES. (Illustrated.) ABALONE OR HALIOTIS SHELLS OF THE CALIFOR- RECENT LITERATURE-The Colorado Formation -Our Native Birds of Song and Beauty- Cartailhac's Prehistoric France-Report of Mineralogy-Crystallization of Enargite- Crystallization of Scolecite and Meta-scolecite -Crystallization of Herderite-Composition and Related Physical Properties of Topaz— Composition of Chondrodite, Humite and Clinohumite-Leucite from New Jersey- Variscite from Utah - Utilization of Auer- bach Calcite for Nicols - Crystallization of Willenice-Composition of Staurolite and Arrangement of its Inclusions-Determina- WILLIAM WESLEY & SON, Owing to the absence of limbs and other points in which diversity is usually apparent, the classification of the snakes has always presented difficulties to the zoologist. An order which dates from Cretaceous time and has spread over the entire world, must have differentiated in structure, if its history has been like that of other orders of Vertebrata. Yet the researches of anatomists have only resulted in finding characters which define five suborders, and about a dozen families. the natural groups thus defined, one family, the Colubridæ, embraces three-fourths of the species, and is of cosmopolitan distribution. So long as this was the principal result attained, it remained clear that the stronghold of the order had not yet been taken. Of The primary divisions above referred to, are defined by peculiarities of the skeleton, and these were mostly originally described by Johannes Müller. In the preparation of their Herpetologie Générale, Duméril and Bibron made a full study of the dentition. The results they obtained were important, but they were very far from expressing an exact and clear cut, classification. The greatest defect of their definitions based on the teeth is that they too often fail to define. One type passes by easy gradations into another, so that in many cases it is im possible to determine what type a given dentition represents. In most cases it is clear that, among Colubrid snakes at least, no higher groups than genera can be predicated on dentition, and frequently not even these. Under such circumstances further structural characters had to be sought for if we are to have any clear idea of the affinities and phylogeny of this curious branch of the Reptilia. In any case no systematic arrangement can be regarded as final until the entire anatomy is known. In 1864' I pointed out that certain snakes, notably the water snakes, have the vertebral hypapophyses continued to the tail, as in the truly venomous forms. Boulenger has since found this character in a good many forms which I had not examined, and which have no affinity to the water snakes. This character, while important, presents the same evanescent stages in certain types that the dental characters before noticed exhibit. It had long appeared to me that the only prehensile organs possessed by serpents, the hemipenes, might probably present structural variations expressive of affinity or diversity. In 1893 I examined these structures in many of the leading types, and was gratified by the discovery of a great many structural characters. In fact these organs exhibit a variety of ornamentation and armature beyond any part of the anatomy in the Ophidia, and I am satisfied that they furnish more important indication of near affinity than any other part of these reptiles yet examined. No one hereafter can be sure of the place of a serpent in the system until the hemipenis has been examined. Still another part of the structure remained to be studied. The assymmetry of the lungs of snakes had often been noted by anatomists, but very little was known as to the range of variation. Accordingly the present year, I undertook a study of the pulmonary organs. I was able to confirm observations previously made by Schlegel and Stannius, and to correct some others, and to add a great number of facts as to species not 1 Proceedings Academy of Natural Sciences, Philada. 2 American Naturlist, 1893, p. 477. 3 Proceeds. Amer. Philos. Soc., 1894, p. 217. previously examined. I cannot give here all the details observed, for which I refer to the papers quoted, but I give a general view of the results. One of these is that I am able to confirm the conclusion of Boulenger; i. e, that the Colubriform venomous snakes, the Proteroglypha, (cobras, Elapes, etc.), do not differ in any fundamental respect from the non-venomous Colubridæ, and that they can not be characterized as a suborder. The suborders then are: Catodonta (Type Glauconia). Tortricina (Ilysiidæ and Rhinophidae). Colubroidea (Peropoda, Asinea, and Proterogylpha). The hemipenis is a projectile organ in the form of a hollow tube whose base is on one side of the middle line, and which opens into the anus. When retracted it lies beneath the tail, extending for a greater or less distance, and terminating in a cylindrical muscle. This has considerable length, and is finally inserted on a caudal vertebra. When the organ is projected this muscle is drawn forwards, so as to evaginate the tubular organ. Thus the inside of the tube becomes the outside, and the entire organ projects freely from its base anteriorly. It finds its way into the corresponding oviduct of the female (Plate XXVIII, v), and when once in place it cannot be tracted in most species, without invagination. This is per formed by the contraction of the now internal retractor muscle. This is inserted on the internal face of the apex, and draws it inwards, so that it soon assumes the original ensheathed position beneath the tail. It cannot be withdrawn from the oviduct without invagination, because it is generally set with strong bony spines which diverge backwards. They have a perfect grip on the walls of the oviduct, and would in some instances lacerate that organ if the two bodies should be forcibly drawn apart. In other cases the hemipenis would be torn off at the base. Snakes sometimes partially project this organ, apparently in some instances for defence, as the spines are very pungent, and are sometimes curved like cats claws. Such at least would seem to have been the |