DESCRIPTION OF THE SPECIES OF PTERYGOTUS 227 
ing in a blunt point. The margin of this and the preceding joint are 
minutely serrate. 
Locality. — Lesmahago, an abundant species. (Collected by 
Mr. R. Slimon.) The specimens are all in the Museum of Practical 
Geology. 
PLate I. [PLate 12] Fic. 17. 
EURYPTERUS LANCEOLATUS. 
Gen. Cuar.' Euryprerus, Dekay, 1826. Body as in Prerygotus, with 12 
segments, eyes subcentral, antennz without chele. 
E. elongatus, postice attenuatus, articulis 12, quorum 10 transversis, pen- 
ultimo oblongo ; cauda acuté product, ad basin tumidd. 
SynonyM. Aimantopterus lanceolatus, SALTER, in Quart. Journ. Geol. 
Soc, lc. p. 28, fig. 5 (¢ar/ joint). 
Perfect, except the carapace, which, when the plate was engraved, 
was supposed to have resembled that of P. acuminatus. It is, how- 
ever, almost certainly an Eurypterus, from the elongate-linear caudal 
joint, but the shape of the swimming feet is more linear than usual 
in the genus. It is here figured because of its association with the 
Pterygoti in my former notice. 
Body two and a half inches long, by three-quarters wide in the 
broadest part, which is about the fourth segment; from thence it 
tapers very gradually to the last. The anterior segment is narrow 
(short), not above one-fifth as long as wide, with its ends recurved ; 
the next, not much broader, is straight posteriorly. The last thoracic 
ring (sixth) is three and a half times as wide as long, with the 
posterior angles a little produced ; from thence the joints are larger 
and less transverse, the tenth being only half as wide again as 
long. The penultimate joint is about as long as wide, but narrowed 
posteriorly. 
The terminal joint (telson) is three-quarters of an inch long and 
only two-tenths wide; it is regularly conical and acute, has a median 
keel (apparently tumid at the extreme base) nearly all the way down, 
and also one along each edge. 
1 For remarks on the generic character of Zus-ypterus, see pp. 200, 204. It differs from 
Pterygotus chiefly in the subcentral eyes, but also by the want of the large chelz to the 
antenne. 
It is hoped to illustrate this genus in a future monograph, meanwhile the reader is referred 
to the Quart. Journ. Geol. Soc., vol. xv., for information on the species. 
Q 2 
