61 
from the external margin, is, in a very small degree, 
depressed, and displays a number of broken and con- 
tinuous striz, parallel to that margin. There are no 
traces of organs of vision. The buckler is nearly the 
segment of a circle; anterior edge, in the present 
_ €ase, imperfect; it is four inches and three-fifths 
broad, and one inch and one-ninth long at the centre; 
it joins the abdomen by a somewhat sinuous trans- 
verse line; cheeks and front of equal breadth; the 
former are flat, but rise at the sharp ridge by which 
they unite with the front; they are triangular in 
shape; their outer angles terminating by an acute 
tip. The strize mentioned above are here not quite 
parallel to the-external border; the front is a shallow 
depression; rounded but tapering anteriorly; it is in- 
tersected from above on each side obliquely towards 
the mesial line, by a ridge bifurcatine downwards; 
another smaller ridge nearly bisects the front perpen- 
dicularly. | : 
The abdomen and post abdomen are not distinct. 
The abdomen exclusive of the cauda is three inches 
and a half long; it exhibits fourteen cost varying 
indiscriminately from one-fifth to one-fourth’ of an 
inch in breadth, except the three inferior ones, which 
are rather broader; they occupy the whole abdomen 
without membranaceous interspaces, and are sepa- 
rated by a black sulcus, not always well defined, and 
sometimes a line in diameter. Each costa is canali- 
culated from the upper and under angle to the tip. 
The middle lobe is separated from the lateral’ by a 
shallow, rude sulcus, which however, does not al- 
F 
