616 MR. SCLATER ON THE © [June 16, 
“perforated ” fang of laps 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 pre- 
sence 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 Viperide 
(Causus, t. c. p. 466) we 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 me that 
the Viperids have been derived from the Opisthoglyphs, and that 
there is no direct genetic relationship between them and the Pro- 
teroglyphs, contrary to the old view which represented the Elapines 
as forming the passage between the Colubrines and the Viperines. 
We have thus traced a nearly complete filiation, so far as the jaws 
and teeth are concerned, between the Colubride aglyphe and the 
proteroglyphz on the one hand, and between the former and the 
Viperide on the other. 
Mr. West points to structural differences in the poison-glands 
between the Opisthoglypha and the Proteroglypha. It will bea 
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. Frowsr, 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 Mr. 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 Gnu (to which the specimens now living in the Society’s 
Gardens belonged), which consisted mainly in the generally 
brownish colour cf the fur and the broad whitish band across the 
face above the eyes, and proposed for it the subspecific name Con- 
nochetes taurinus johnstoni. From the British-East-African form 
