194 
Records of the Geological Survey of India. 
[vol. x. 
On both sides of the median line of this seventh segment are seen two oblong spaces, 
beginning broader at the base of the segment, and becoming very attenuated towards the 
apex; their extension is very well characterised and defined by closely set, sharply marked, 
minute holes, like pricks of a needle. I suppose these two spaces are the impressions of two 
similar ridges, which in the living animal were in this place on the upper surface. 
On both sides of this seventh segment are the caudal plates, two of them on each side, 
and they form, together with the median seventh segment, a pentaphyllous caudal fin. These 
caudal plates are connected by a special intervening segmental portion with the sixth 
segment. Their form is broadly, sub-quadrately oval; and they are, as far as I can observe, 
traversed by a longitudinal ridge—in our specimen, of course, very flattened. 
On one of the outer plates (in the drawing the right one) I can observe, nearer the 
apical margin (the extremity), a curved line, which, I suppose, represents a suture in this plate. 
This would agree with Mr. H. Woodward’s observation on Eryon Barrovensis (1866, l.c., 
p. 496), while Dr. Oppel (1862, l. c., p. 9) stated that the caudal plates are undivided, as is, in 
fact, the case with the forms from the “ Solenhofen-Schiefer.” Mr. H. Woodward marked this 
suture in the caudal plates as an important distinction of Eryon Barrovensis, from the 
Solenhofen species ; and the character must be used to the same extent in our specimen. 
On the inner caudal plates, I could observe that their margin is finely denticulated. The 
whole surface of the abdomen, as preserved in our specimen, shows very fine minute holes, 
which extend also into the tubercular impressions in the median line of the segments. 
These little holes are only the impressions of little warts which covered the epidermis 
of the living animal. 
The lateral processes (epimera) of the segments are a little decreasing in size towards 
the last segment, and are rounded in their anterior marginal portion. The process of the 
last segment is more acuminate; and to this are joined the segmental portions, on which the 
caudal plates are inserted. These lateral processes show also the minute holes, which I 
mentioned before to be found on the whole surface. 
Dimensions of the abdomen. 
Mm. 
a. From the posterior margin of the carapace to the apex of the 7th segment ... ... 48’0 
b. Length of 1st segment ... ... ... ... ... ... 3-5 
c. of 2 nd ... ... ... ... ... ... -5 
d. of 3rd „ ... ... ... ... ... ... -e 
t. „ of 4th „ ... ... ... ... ... ... *6 
/. „ of 5th „ ... ... ... ... ... ... *6 
g. „ of 6 th „ ... ... ... ... ... ... 5 5 
h. „ of 7th „ ... ... ... ... ... ... 16*0 
Breadth of the same at base ... ... ... ... ... ... n*o 
t. Breadth of inner caudal plates ... ... ... ... ... ... 8*5 
Length of the same ... ... ... ... ... ... ... 14-0 
k. Length of outer caudal plate from point of insertion to the apex ... ... 16'5 
l. Greatest breadth of the same ... ... ... ... ... ... iro 
m. Distance of suture in the caudal plate from point of insertion ... ... ... 1 T 5 
n. Breadth of 1st segment ... ... ... ... ... ... ... 28'5 
Compaeison. —The very flat and broad carapace, the structure of the seven segments 
with median and lateral tubercles on the anterior margin, the form and structure of the 
caudal plates, leave no doubt that our specimen is an Eryon. The two most closely related 
forms arc Eryon Uurtmanni, v. M., and Eryon Barrovensis, McCoy. The general resem¬ 
blance is very close. 
Eeyoit Haetmanni is figured by H. v. Meyer in N. Act. Ac. Leop. Carol, vol. xviii. 
pt. i, pi xi-xii. This species is, however, much larger in all dimensions, although the 
general form of the carapace would agree. The segments are much broader and longer; the 
