| OCR Text |
Show 616 MR. SCLATER ON THE [June 16, " perforated " fang of Elaps proper (t. c. p. 411), in which all other maxillary teeth have disappeared and the palatal and mandibular teeth are much reduced in number. In other genera of the same group the posterior maxillary teeth persist and may all acquire feeble grooves, as well as the anterior mandibular teeth (Glyphodon, p. 313). In the Proteroglyphs adapted to life in the sea, a similar series of modifications takes place. From the Aglyphodont forms, in which the teeth increase in size posteriorly, we are gradually led to the Opisthoglyphs, which are only to be distinguished by the presence of more or less deep grooves on the posterior fang-like teeth, the series culminating in such forms as have the maxillary bone much abbreviated, the solid teeth reduced to two or three, and the fangs extremely large and deeply grooved (Miodon, t. c. p. 250). If we then turn to the skull of the least specialized among the Viperidse (Causus, t. c. p. 466) w e see that the poison-fangs are situated on the posterior extremity of the maxillary, close to its articulation with the ectopterygoid, a condition which is identical with that of the Opisthoglyphous Colubrids. It is therefore clear to m e that the Yiperids have been derived from the Opisthoglyphs, and that there is no direct genetic relationship between them and the Proteroglyphs, contrary to the old view which represented the Elapines as forming the passage between the Colubrines and the Viperines. W e have thus traced a nearly complete filiation, so far as the jaws and teeth are concerned, between the Colubridae aglyphae and the proteroglypha? on the one hand, and between the former and the Viperidse on the other. Mr. West points to structural .differences in the poison-glands between the Opisthoglypha and the Proteroglypha. It will be a matter for future investigation to ascertain whether he is justified in his assumption that the gland is homologous in these types or whether it has not been independently developed. June 16, 1896. Sir W . H . F L O W E R , K.C.B., LL.D., F.R.S., President, in the Chair. Mr. Sclater exhibited a drawing (Plate XXVIII.) of the Gnu of Nyasaland, taken by M r . Caldwell from the specimen recently transmitted to him by Sir H . H . Johnston (see above p. 506), and now placed in the British Museum. Mr. Sclater pointed out the differences between this form and the ordinary form of the Brindled G n u (to which the specimens n o w living in the Societys Gardens belonged), which consisted mainly in the generally brownish colour of the fur and the broad whitish band across the face above the eyes, and proposed for it the subspecific name Con-nochaetes taurinus johnstoni. From the British-East-African form |
