Dr. H. Woodward—Eurypterus in the Coal-Measures. 281 
median appendage to operculum 8cm., breath 4cm.; breadth of 
1st abdominal segment 14 cm., length 7 cm.; metastoma, length 10 cm., 
-breadth 7 cm. 
In the specimens of Zurypterus, figured and described by Professor 
James Hall from Pennsylvania, the body- segments, especially those of 
the abdomen, appear to be more narrow and elongated than these 
Derbyshire specimens indicate. 2. Mloyseyi, for instance, has a more 
globular or rotund thorax, and the ornamentation is less spinose and 
the squame are more minute. 
The thoracic ségments figured by me (see Gror. Mac., 1888, 
pp. 419-421) from the Coal-measures of Radstock, Somerset. evidently 
belonged (like the Scottish specimen named /. seabr osus) to a much 
larger form, at least twice, if not thrice, as large. 
Evryrrerus Dersrensts, sp. nov. (Pl. XIII, Fig. 3.) 
This specimen is much smaller than the preceding examples and 
not very clearly preserved, being mixed with numerous detached and 
broken leaves of a fern; nevertheless, although at first doubtful, 
I am now inclined to regard it as being certainly distinct from 
£. Moysey?, with which it was found associated. 
The head-shield has. the usual subquadrate form, rounded in front ; 
the eyes, which are prominent and a little larger in proportion to 
its relative size, are placed somewhat closer together, and rather 
nearer the anterior margin than in EZ. Moyseyi. Two imperfect 
endognaths (ev.) are seen on the right side of the head and one of 
the swimming feet (ec.) on the left side. The metastoma or post-oral 
plate (m.) is oval in form, its posterior border being hidden beneath 
the thoracic segments, which are squeezed together somewhat and 
have lost a part of their margins. ‘There is a faint impression on 
the counterpart (not drawn) of a long median appendage belonging 
to the opercular plate seen beneath the thoracic sternites. What is 
very interesting is the presence of about six narrow but deep 
abdominal segments, having a crenulated ornamentation suggesting 
the presence of a row of marginal spines along the posterior border 
of each tergite. Similar plice are represented by James Hall in 
Fi. Mansfieldi (op. cit., pl. iv, fig. 3; pl. v, fig. 3; and pl. vi) from 
Pennsylvania. 
Dimensions.—Total length of specimen 30 centimetres, greatest 
breadth of thorax 12cm.; breadth of head 10cm., length of head 
6em.; length of thorax 9cm.; length of abdomen 15cm.; breadth of 
anterior segment 8 cm., length 4 em. 
This specimen (Fig. 3) differs slightly in the form of the head- shield, 
which is rather more quadrate than in Figs. 1 and 2; the body is more 
slender, and the plice (or spities ?) along the posterior border of 
the abdominal segments are not seen on the posterior somites 
of Figs. 1 and 2. “Possibly this might be considered as the male of 
the lareer species, but the only other evidence is in the form of 
the imperfectly indicated median appendage of the opercular plate. 
Against this, however, is the fact that Figs. 1 and 2 differ probably 
quite as much from each other in the form of the opercular plate, 
and therefore Fig. 1 might equally well be deemed to be the male 
and Fig. 2 the female of the same species. 
