58 ICHTHYOLOGY 
are subject to very great variations. Those on the sides of the 
pectorals, that I had only seen on young specimens, belong to. 
the male sex, and are placed in two or three series. The 
orbit spines are equal in both sexes, but in one female they 
form also a transverse line behind the orbits; the line 
of strong spines which extend on the median line of the back 
does not sometimes extend to the anterior part of the body 
the disc is generally covered with very small spines, placed far 
apart one from the other, but in some specimens it is almost 
entirely smooth, and the lower parts are always so ; the tail 
is more or less covered with large spines, which form from one to 
four longitudinal series on the centre, without taking in 
account the small slender arched ones, which are very 
numerous. 
MYLIOBATIS NIEUHOFII. 
In my last year's paper, I stated that two sorts of Mylobatis 
were found in the Melbourne sea, but I now believe that they 
must be all united under the present name. 
The documents I have at my disposal are : 
1. Two small specimens, with cross blue bands, similar to 
the one I described. {Proceedings, p. 226.) 
2. The mouth of a large specimen. 
3. A large specimen, forty-two inches long. This has no 
traces of transverse bands, and the tail is proportionately 
rather shorter and thicker than in the small specimens ; its 
caudal spine is four and a-half inches long. 
I believe that the young Australian specimens of M. Aquila 
mentioned by Dr. Gunther, belong to this sort, which attains 
enormous dimensions, and sometimes, it is said, weighs up to 
two thousand pounds. 
