1886. ] Zoology. 175 
terior dorsals and the sacrals, and I can confirm his observations. 
—Dr. G. Baur, Yale College Mus., New Haven, Conn., Dec. 19, 
1885, 
THE INTERCENTRUM IN SPHENODON.'—Researches into the em- 
bryology of the Urodela and Anura have not yet brought to light 
any traces of the rhachitomous structure; a condition of things 
which is probably due to ccenogeny or falsification of the embry- 
onic record—a phenomenon which is not uncommon. There can 
be no doubt, however, that the entire record was presented in the 
embryonic history of Permian land Vertebrata, and for a long 
period subsequently, but that the rhachitomous stage has: been, 
with the true centrum, lost from the batrachian line at least. The 
only existing reptile which could be expected to show important 
traces of the ancestral, or embolomerous stage, is Sphenodon. This 
genus, as is well known, is the living representative of the order 
Rhynchocephalia, the nearest order to the Theromorpha. Having 
fortunately a specimen in alcohol, presented to me by Dr. Hector, 
the able director of the Geological Survey of New Zealand, I 
examined the caudal vertebre to determine the connections of 
the chevron bones. I find these to be attached, not principally 
in press. 
The centra differ much from those of Cricotus in their form, 
resembling in outline those of the Pelycosauria. They however 
have the vertical median partial suture seen also in the Lacertilia, 
as already described by Günther. The caudal vertebra are so 
gradually modified as we followed them forwards, however, as to 
make it probable that these halves do not represent any of the 
elements of the rhachitomous column besides the true centrum. 
_l add that there is probably a hypocentrum pleurale in the cer- 
vical region of the rhachitomous Eryops. They become ossified 
early with the posterior side of the intercentrum in front of 
m.—. . Cope. 
On THE Tarsus or Bats.—In the course of some recent obser- 
vations made upon the tarsus of bats, I ascertained that the astrag- 
alus and calcaneum were elongate, and exhibited the general 
characters of these bones in mammals in which little or no weight 
‘On the Batrachian Intercentrum, NATURALIST, 1866, p. 76. 
*Since the above was written, Vol. 11, pt. 11, of Fritsch’s Fauna der Gaskohle has 
come to hand. It contains a note on the intercentra of Sphenodon. : 
