DESCRIPTION OF THE SPECIES OF PTERYGOTUS 251 
surface: and it quite possibly belongs to P. /udensis, or even to a 
new species. 
Penultimate Joint, Plate XIV. [Plate 25] fig. 18—Of this we 
have only the lower surface ; and as the plice are restricted to the 
upper portions, and only a few small ones are interspersed, it is 
possibly not P. problematicus, but of the same species as fig. 15, 
mentioned above. The width is greater than that of the same joint 
in P. anglicus or P. ludenszs, being three inches and a half, while the 
length is only two and a quarter, (or as fourteen to nine,) which 
is about the proportion in P. gigas. The joint is not expanded 
posteriorly as in that species, and the plicae are semicircular, not 
pointed, on the lower side.] 
In the true Ludlow Rock but few body joints have been met 
with, the two best are figured from Mr. J. Harley’s collection, viz.,. 
Plate XII. [Plate 23] fig. 20, must be one of the thoracic rings, and 
fig. 21, probably the tenth or last but two of the segments. Both 
show the minute interspersed plice very clearly, and these small 
plicee extend over nearly all the segment, while the larger ones are 
confined to the anterior half. 
Telson, as yet unknown, as also is the epzstomzan plate. 
sintenng, Plate NII. [Plate 23] figs. 7-10. — Fig. 10 is most 
probably part of the stem, and shows the large and small plice in 
perfection. Figs. 7 to 9, the large characteristic chele, which can 
scarcely be confounded with any other species, the teeth being so 
much elongated. Fig. 7 is the fixed claw, with a widely expanded 
and largely dentate base.! The shaft is parallel-sided (not tapering 
as in P. /udensis), and the teeth long-lanceolate, the large one being 
much longer than the diameter of the shaft, (in fig. 7, fully three- 
quarters of an inch long,) the secondaries three or four on each side 
of it, with small teeth interspersed, all linear-lanceolate, erect and 
remote, not crowded at their bases. In the fixed ramus they are 
either erect or (fig. 8) point forward a very little. 
The striz on the teeth are very fine and close,’ oblique some- 
1 See P. ludensis (Plate XIV. [Plate 25] fig. 10), for a similar chela. 
2 See also Strickland’s figure, quoted above. There is one lanceolate fragment (2 4) in 
that figure, here reproduced, fig. 9", which is striated finely like the teeth. It is serrated 
all down one side. Its nature is quite doubtful ; but it is associated with the antenna; and 
as the large primary tooth in P. gigas (Plate IX. [Plate 20] fig. 3) is serrated posteriorly, 
it is possible this may be the case in one of the chel of the present species. There is a 
small conical uncinate appendage in the same figure, Geol. Journ., that is yet unexplained. — 
Quart. Journ. Geol. Soc., 1. c. 
