RAYS. 
319 
classes, both fresh and salted ; the females and 
young are called Maids, and are considered best 
for the table. The flesh is in best condition in 
autumn and winter; becoming soft and woolly 
in spring and summer, which is the spawning 
season. Great numbers are caught, however, at 
these times, their approach to the shore render- 
ing their capture more easy. 
The acute spines with which so many of the 
Rays are studded, make them dangerous to 
handle ; no doubt they may be considered as 
weapons of defence, if not of offence. It is 
observable that the long and flexible tail is 
always the most effectively armed : we have 
already seen how the spine of the Trygon is 
used ; the learned zoologist to whom we are 
indebted for that information, has also described 
the defensive action of the Skate. The point 
of the nose and the base of the tail are bent 
upwards towards each other: the upper surface 
of the body being then concave, the tail is lashed 
about in all directions over it, and the rows of 
sharp spines frequently inflict severe wounds.” 
Family IV. Petromyzonid^. 
{Stone-suckers,) 
We have now arrived at the lowest examples 
of organization among Fishes, and consequently 
the bottom of the scale formed by the series of 
animals having an internal skeleton of bone and 
a vertebrate d spine. Throughout the whole of 
this Order we have seen how the former charac- 
ter has become less and less distinct, the skeleton 
