No. 421.] KANGAROO RATS IN CAPTIVITY. 49 
jumping mice (Zapus) ; 13 of the former are of the genus Dipo- 
domys and 10 of Perodipus, the genus to which our present 
subject belongs. (See pp. 236, 237; Family (VI) Heteromy- 
idee; and for three views of the skull of Perodipus agilis, 
p- 2 Other genera of this extensive group of our smaller 
rodents have likewise been largely added to, and a great many 
new species described of recent years. Mr. Elliot has since 
published a supplement to the volume here referred to, and 
this contains the descriptions of still other species. 
I found my specimens of P. richardsoni extremely gentle in 
disposition, and any one of them would allow me to catch hold 
of it with my hand, and no amount of handling or even gentle 
squeezing could induce the little animal to bite or scratch. On 
one occasion I let them all out in my study, when it was very 
amusing to see their various antics and capers. They were as 
full of fun and play as could be, and soon seemed to take a 
genuine delight in my attempts to recapture them. They 
hopped about with great agility on their hind pair of kangaroo- 
like legs, while the little short pair of anterior limbs were 
curled inwards on the chest. At these times the animal’s tail 
is simply dragged behind it, being in contact with the ground 
for its entire length. Its body is held obliquely, its axis making 
rather a small angle with the surface over which it is passing, 
but if occasion occurs for it to use its fore legs, they are 
brought into play at once, either for feeding, climbing, or 
burrowing. They are able climbers, and the rapidity with 
which they can dig a burrow in ordinary ground is astonishing. 
They use the fore feet to perform the digging part and the 
long and strong hind legs to kick the loosened soil out of their 
way behind, as it accumulates every moment or so. In soft 
soil one of these little mammals can put itself out of sight in 
less than a minute by digging, and it really seems to enjoy the 
operation. Among themselves they are somewhat inclined to 
be quarrelsome, biting and scratching one another sometimes 
without any apparent cause, while at other times they huddle 
together in a corner and sleep as peacefully as so many snails. 
- The borders of the ears of one of these males, however, exhibit 
a few small healed-up nicks and notches that have very much 
Mo. Bot. t Gardou 
