Zoology. 275 
large, thin, gibbous, nearly round, carinate on the. middle of the back, 
deeply emarginate behind, the edges of the emargination fringed with 
Short spines: eyes three, simple, the two anterior larger, approximate, 
somewhat lunate, the third one round, placed in the middle behind the 
: iwo others: antenne very short, inserted near the mandibles, two-joint- 
ed, joints cylindrical, subequal, the second joints somewhat accuminate 
and naked at the tip: first pair of feet, or as they have been called, 
exterior antenne, furnished with four articulated filaments; of these 
filaments, the outer one is longer than the body, the next half the length 
of the first, the third about one-third the length of the second, and the 
fourth very short: the other feet, amounting to ten pair, are flattened, 
trifid at the tip, the intermediate division being the longest, furnished 
on the inner side with a short branch, and externally with a broad lam- 
_ Ina; below these feet are twelve pair of laminz, the five anterior pair 
larger, the seven smaller pair reaching to the vent, which is covered 
by the last pair; these lamine are complicated in their structure, and 
ciliate with short hairs: tail long, consisting of sixteen joints counting 
downwards from the vent, the last one the longest, somewhat coria- 
ceous, emarginate and ending in two long articulated naked filaments ; 
- the joints of the tail and of the filaments are furnished each with a row 
of small spines, which run entirely round. 
Length to the end of the tail, 1-5 of an inch—of the buckler, ‘65— 
= eadth of the same, 7.. ; 
~ OF the habits of this animal, we know but little ; it was found in im- 
mense numbers in a small shallow lake on the high plateau between 
— 4008e-pole creek and Crow creek, northeast of Long’s peak, in th 
Rocky Mountains : they were swimming about with great activity, 
Plunging to the bottom and rising to the surface. All of them that were 
caught appear to be males, at least none of them have any ova attach- 
ed: the common species in Europe, A. cancriformis, on the contrary, 
- has never been found but of the opposite sex. ey 
: 9: The Soft Bodies of Polythalamia found in a Fossil State—In a 
____ Microscopical examination of chalk and flint by Dr. Mantell, published 
eo. last August in the Annals of Natural History, it was announced for the 
oS first time, that the soft parts of foraminifera occur in a silicified state 
inthe flints of the southeast of England.’ Dr. Mantell has followed up 
a “: his researches, and has succeeded in obtaining the internal soft parts of 
_ Tolalie, in the state of a dark brown carbonaceous substance, retaining 
~ the perfect form of the interior of the shell:in which, when the animal 
Was living, they were enclosed. ‘This discovery was made by immer- 
‘sing chalk in weak’ hydrochloric acid, by which process not only the 
: litte, but the éalcareous. shells the earth contained, were dissolved ; the 
um being only grains of white and green transparent quartz, and 
. 
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