NA TURE 



;i3 



THURSDAY, AUGUST 3, 1893. 



A CATALOGUE OF SNAKES. 



Catalogue of the Snakes in the British Museum {Natural 

 History'). Vol. I. By George Albert Boulenger. 

 (London: 1893.) 



IN the present volume Mr. Boulenger, the author of 

 the Catalogues of Batrachia, and of the Lizards, 

 Tortoises, Rhynchocephalians and Crocodiles, amongst 

 the Reptilia, commences the description of the only 

 order of living reptiles not hitherto treated by him 

 in the octavo series of British Museum Catalogues. 



The Ophidia, whether regarded as a distinct order, as 

 they appear in the text of the catalogue, or as one of the 

 suborders of Squamata, with the Lacertilia and Rhipto- 

 glossa (Chameleons) forming the other sub-orders, as 

 advocated in a foot-note, are by far the most important 

 group of living reptiles after the lizards, and are, like the 

 latter, of comparatively recent origin. No remains of 

 true snakes have been recognised in deposits older than 

 upper cretaceous. 



Few groups of vertebrate animals have proved as 

 difficult to classify correctly as snakes. The absence of 

 limbs and the peculiarly specialised (elongate form 

 have made species, genera, and even in some cases 

 families resemble each other far more exactly than is 

 usually the case. The result in this and in some similar 

 instances has been that characters of little or no intrinsic 

 value have long been regarded as distinctive, and that an 

 artificial system has been adopted. Certainly in the case 

 of the snakes there was every excuse for characters 

 which are now known to be adaptive and of secondary 

 value in classification, being long supposed to be of 

 primary importance, for the principal of these characters 

 consisted in the presence or absence of weapons by 

 which the life of large animals, including man, could be 

 destroyed with extraordinary rapidity. The first inquiry 

 naturally made by any person confronted by a snake is 

 "Is it poisonous?" and as the question whether the 

 animal can or cannot inflict an injury that may be, and 

 very often is known to be, fatal, can be certainly decided 

 by examining the structure of the teeth, it is far from 

 surprising that that structure should long have been 

 accepted as the criterion for dividing snakes into primary 

 groups. It was of course recognised that vipers and 

 rattlesnakes, which present marked external differences 

 from such poisonous serpents as the cobra, must be kept 

 distinct from the latter, and consequently all ophidians 

 were until quite recently divided into three groups, (i) 

 harmless snakes ; (2) venomous colubrine snakes, and 

 (3) viperine snakes, both the two latter, or poisonous 

 sections, being distinguished by having a grooved or 

 perforated tooth situated at the anterior extremity of the 

 maxillary on each side, and supplied with a poisonous 

 secretion from the very slightly modified salivary 

 gland. 



But it had long been known that amongst the so-called 

 harmless colubrine snakes there were several genera such 

 as Dipsas, Psammophis, and Homolopsis, with grooved 

 teeth exactly similar in structure to those characteristic 

 •of poisonous forms, but situated at the posterior instead 

 NO. 1240, VOL 48] 



of the anterior termination of the maxillary. These 

 snakes, the Opisthoglypha, as they are termed, were kept 

 apart from other colubrine snakes by several herpeto- 

 logists, but it is only within the last few years that their 

 poisonous character has been distinctly ascertained. It 

 is true that owing to the position of the grooved fangs, 

 and also to the small quantity of poisonous secretion, the 

 bite of these snakes is harmless to man and to the larger 

 animals, but it has been ascertained that some of them 

 certainly, and probably all, paralyse or kill the small 

 mammals or other animals on which they feed. 



The last few years too have shown that grooved teeth, 

 connected with a poison gland occur in the mandible of 

 a lizard (Heloderma), and this recurrence of the same 

 kind of tooth in different positions, and in very distinct 

 reptiles destroys the value of the character as evidence 

 of genetic affinity. But if the distinction between 

 poisonous and non-poisonous snakes is disregarded, the 

 differences between harmless colubrines (Aglypha), such 

 as Tropidonotus, and the forms with grooved teeth, like 

 Dipsas or Homolopsis (Opisthoglypha), Naja or Elaps 

 (Proteroglypha), are insufficient to justify placing them 

 in separate subdivisions of the group. 



Three years since, in his work on the Reptilia and 

 Batrachia of British India, Mr. Boulenger rejected the 

 old division of snakes into venomous and harmless, and 

 proposed a new classification of the whole group founded 

 on the characters of the skull, and the presence or 

 absence of particular cranial bones. The occasion was a 

 good one, for, singular to state, India is the only country 

 in the world where all families of snakes are represented. 

 Time only can show whether the present classification 

 will stand; it is far from improbable that future discoveries 

 may result in some modification of the system now 

 adopted, but there can be not the slightest question that 

 the principle is sound, and that the present system is a 

 distinct improvement on its predecessors. The whole 

 order of snakes is, by Mr. Boulenger, divided into the 

 following nine families : (i) Typhlopidas, (2) Glauconiidas, 

 (3) Boidae, (4) Ilysiidas, (5) Uropeltidas, (6) Xenopeltidse, 

 (7) Colubridse, (8) Amblycephalidas, (9) Viperidffi. 



Of these only three are generally known — (i) the Boidas, 

 containing the boas, pythons, and the curious Eryx, the 

 two-headed snake of Indian jugglers ; (2) the Viperidae, 

 which comprise ordinary vipers and Crotalinse, (rattle- 

 snakes and their allies) ; and (3) the Colubrida, which 

 play much the same part amongst snakes that the 

 Passeres do amongst birds, and form a considerable 

 majority of the living species. In the Indian list, out of 

 264 known snakes, 182, or about two-thirds, belong to 

 the Colubridas, and probably a similar proportion will be 

 found to prevail throughout the world. The Colubridffi 

 are in fact the dominant type of the present time. They are 

 in all probability of comparatively recent origin, and the 

 generic distinctions amongst them are frequently small 

 and difficult to recognise. 



Of the care bestowed upon the present work it is diffi- 

 cult to speak too highly. One instance may be quoted, 

 as it illustrates the author's anatomical research, and at 

 the same time shows the light thrown on other biological 

 inquiries by accurate systematic knowledge. The snake 

 fauna of Madagascar has long been known to present 

 some remarkable peculiarities. The other reptiles and 



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