On the markings of the Carapaz of Crabs. 97 
divides it into two parts longitudinally. "This is an important 
specific eharaeter and though hitherto unmentioned in descrip- 
tions, it is easily desciibed when a proper notation is adopted. 5L, 
also subdivides from above downward or rather obliquely inward. 
3M. subdivides at times into 3 parts as shown in figure 2 which in- 
cludes also 4M. Figure 3 represents another form of this areolet 
and AM. In a still further subdivision, each of the areolets 
is reduced to tubercles, some of them consisting of-but one, 
and others of three or four. Figure 4 represents the medial 
region of the Lagostoma modosa ; the preemedial is a. single tu- 
bercle; the extra-medial consists of 7 tubercles, 9 in an inner 
and 4 in an outer series ; the intra-medial includes 4 besides 
some smaller; and the post-medial includes 2 large and some 
smaller tabercles. When the subdivisions are not carried as far, 
a portion may be separated anteriorly from each half of 2M, while 
the rest remains entire. 
It is common for 1R to have a tubercle or two on its surface 
or areolets in the same transverse line with the tooth. 
T'eeth of the autero-lateral margin.—'The teeth of the margin 
are normally five in number, commencing with the post-orbital 
as the first. 'l'hese five are represented in figure 1, and are desig- 
nated in order by the different letters of the word dentes (or dents 
in Freuch) D, E, N, T, S. Each tooth 1s often separated from 
the adjoining by a minute suture at the bottom of the indentation 
betweeii them, and hence the letters always mark rather a lobe 
of the margin than simply a tooth. 'T'hese teeth vary by obso- 
lescence or subdivision, like the areolets. 
In o5solescence, the tooth E; (second) is the first to disappear, 
this reducing the apparent number to four. 'Then N fades out, 
then T, leaving S alone which may also be wanting. Again S 
is sometimes smaller than 'T' and even disappears. 
In the multiplication of teeth, there is often, as a first addition, a 
tooth s^ (or two s'/, s^,) posterior to S. "There is often also a 
tooth (Z^) between D and E on a lower level than D. But the 
multiplication is generally dependent on the subdivision of the 
normal teeth E, N, 'T', in addition sometimes to S and D,—each 
of these teeth consisting of two or three teeth, either all equal or 
one more prominent. In order to determine the normal relations 
of the teeth when the number is large, we have a guide in the are- 
olets adjoining when they exist; for the areolet AL (or the range 
6L, 5L, A4L,) terminates against tooth or lobe TT, having about 
idi a 
PE EUNT RAN 
