36 BRITISH FOSSIL CRUSTACEA. 
of obtaining a correct idea of the general form of the body and the position of the 
appendages, entire specimens, such as the foregoing, are invaluable, we must not, there- 
fore, omit to study carefully the far more numerous detached portions which have been 
met with, and the separate parts of appendages, as they not unfrequently offer details less 
clearly seen in the more perfect remains. 
We have only to turn over the first seven plates, and especially to note the beautiful 
series of appendages figured in Plate VII," to be convinced of their great value, not only. 
in enabling us to complete our knowledge of the anatomy of these very ancient Crustacea, 
but also accurately to ascertain their proportions. 
The Carapace.—At the period of the publication of Messrs. Huxley and Salter’s 
Monograph the only examples of the carapace of this genus were in the collection of 
Lady Kinnaird.” One of these curious flattened plates is figured at plate iii, fig. 1, of 
that work, which led to the conclusion that the head-shield was trapezoidal in form when 
perfect (op. cit., p. 11); but the tolerably perfect detached head figured on Plate I, fig. 2, 
shows a decidedly semicircular front, as is also well seen in the head of the nearly entire 
but smaller specimen (Plate II, fig. 1), m which the posterior angles are also considerably 
rounded off where the carapace is united to the thoracic somites. 
The organs of the Head—\n speaking of the paired appendages of the cephalon, we 
shall observe the same order as is given for the restored figures of Pterygotus anglicus, in 
the explanation of figs. 1, and 2, Plate VIII. 
The Hyes.—Both the detached head on Plate I, fig. 2, and that on Plate I, fig. 1, 
exhibit the large convex marginal eyes upon the antero-lateral border of the carapace ; but 
I am unable, in these or in any of the other specimens which I have examined, to detect 
the facetted surface of the cornea. Mr. Salter, however, has satisfactorily made them out 
in the specimen from Lady Kinnaird’s cabinet, and says (Mon. cit., p. 68.) —“ The 
lenses are rather large, about eight rows in one tenth of an inch, and in this specimen are 
rhomboidal rather than hexagonal, at least in arrangement; this may be due to pressure 
only.” (See ‘Survey Mon.,’ pl. ii, fig. 1, 1¢, and 14.) Prof. Huxley observes (op 
cit., p. 20)“ Notwithstanding the peculiar character of the markings upon the corneal 
surfaces of these eyes, | wait for better evidence than I have hitherto met with, before 
deciding that they were really compound, and that these markings indicate corneal 
facets.” 
No ornamentation can be detected on the head-shield of the smaller specimen (Plate II, 
fig. 1), but the surface of the larger detached carapace (Plate I, fig. 2), when magnified, 
1 Copied (with the exception of fig. 4) from plates vi and vii of Messrs. Huxley and Salter’s Mono- 
graph on the Lurypterida (1859), from Mr. C. R. Bone’s very excellent figures. 
2 Although these and other specimens are spoken of in the ‘Survey Monograph’ as ‘from tbe col- 
lection of Lord Kinnaird,” I am informed by my friend Mr. Powrie that it is her ladyship who is especially 
devoted to paleontology ; and I therefore beg leave to associate her name with these interesting specimens 
in the collection of which she has taken so much interest. 
