392 DAVISON. [Vol. XI. 



in this region is approximately four hundred and sixty-eight, 

 though some of them near the extremity are rather imperfectly 

 formed. The whole number in the trunk, counting twelve to 

 each vertebra, equals seven hundred and forty-four, which, 

 added to the four hundred and sixty-eight in the caudal region, 

 gives a total of one thousand two hundred and twelve cones. 

 Ill other words, the dorsal and caicdal muscles of this animal 

 have over one tJionsand strong fascial attachnents. 



Having discussed the general structure of these muscles, it 

 is now in order to determine the direction of the fibres. .These 

 are not parallel to a line through the apices of the cones, as we 

 should expect, but are so directed as to form an angle of about 

 ten desrrees with that line. Since there are no cones found in 

 the outer half of the dorsal muscle, the direction of the fibres 

 there is exactly parallel with the axis, being, however, com- 

 pletely interrupted by the inscriptiones tendineae. 



So far as I have been informed, this peculiar conical dispo- 

 sition of the fibres of the dorsal muscle has been observed in 

 only two other vertebrates and in no other Amphibians. Dr. 

 Hair {13) describes similar cones in the alligator, and I have 

 noticed the same structure prevalent in SpJioenodon (Hatteria), 

 the peculiar New Zealand lizard. The genealogical significance 

 of this muscular arrangement will be discussed later. 



The ventral trunk muscles are, as in other Urodeles, com- 

 posed of four sheets of fibres : the transversalis abdominalis, 

 the obliquus internus, obliquus externus, and rectus abdominis. 

 The first named is a mere continuation of the descending 

 lamina of the external dorsal fascia. It may therefore be said 

 to arise from the neural spines, and with its fellow, form a tube 

 inclosing the viscera and dorsal muscles. In other words, the 

 lamina may be considered as an aponeurosis, the muscle-fibres 

 originating just before the aponeurosis emerges into the body 

 cavity. The muscle passes transversely around the ventrum, 

 dwindling again to fascia about one centimetre before joining 

 its fellow along the mid-line. The striking feature in this 

 mnscle is that it is unaffected by the inscriptiones tendineae, a 

 condition not present in any other Amphibian. The obhqnns 

 internns and also the obliquus externus are tJiicker on the left 



