512 TRANSACTIONS OF SECTION C. 
is mainly indebted to H.M. Geological Survey, to Dr. Groom, and to Dr. J. 
Frazer. 
Taking first the forms described by Dr. Callaway, the suggestions of Brogger 
and Linarsson were confirmed as to the following species :— 
Olenus triarthrus, Call. Parabolinella triarthrus, Call., sp. 
Conocory phe monile, Salt. which now } Luloma monile, Call., sp. 
Conophrys salopiensis, Call. stand as Shumardia pusilla, Sars., sp. 
Platypeltis Croftii, Call. Symphysurus Croftti, Call., sp. 
The Shineton Shumardta just mentioned is identical with the Scandinavian 
species, while with Symphysurus Crofti Brogger’s later described S, incipiens 
appears to be identical. 
Of Dr. Callaway’s other species: Asaphellus Homphray?,Salt., the writer referred 
to the genus Megalaspis; and for Olenus Salteri, Call., with which O, Mitchinsont, 
Thomas, is identical, he proposed the name Leptoplastides Saltert, n. sub-gen., 
Call., sp. (See next abstract.) 
Lichapyge cuspidata, Call., based on an isolated tail, is completed, the writer 
believes, by a head and thorax collected by Mr. Rhodes for H.M. Geological 
Survey, and appears, as was inferred by Dr, Callaway from the tail, to be related 
both to Paradonides and to Lichas. 
Of new forms the fauna includes another dAgnostus, A. Callavei, Raw, of 
which a description by the writer has already appeared. Besides the Oleni 
mentioned above, the writer wished to establish another, which, he believes, has 
been confused—the head with P. triarthrus andthe thorax with Leptoplastides 
Salteri. It is very close to, but distinct from, the 7rtarthrus spinosus of Billings. 
It approaches also very closely to the ‘ Peltura’ punctata of Misses Crossfield 
and Skeat, from which it only differs in the possession of spines on the cheeks 
and down the axis, and of this form it may well be the ancestor. This and the 
Shineton form, though bearing a superficial resemblance to the type species of 
Triarthrus, ave yet quite isolated, and should perhaps constitute a new sub-genus. 
For the new form the writer proposes 7riarthrus shinetonensis, n. sp. 
Two new Asaphids have to be recorded: one isa small-eyed Symphysurus, for 
which the name 8. mcrophthalmus, un. sp., is suggested; the other is a new genus 
which appears to connect Mobe and Ogygia, having the tail of the former, but 
spined pleure, approaching those of O. Selwyni, Salt. This was named Desmus 
Cobboldi, n. gen, and sp., and the genus will be found to include some other 
uropean forms. 
A new and strange form occurs, characterised by long spines like wings on the 
fixed cheeks and a tail resembling that of Dicellocephalus (e.g., D. pepinensis), for 
which the name Pterocephalus hemicycloura, n. gen, and sp., is proposed. 
A single tail represents Dicellocephalina furca, Salt., sp., of which it may be 
regarded as a variety, distinguished by its beautifully curved contour. 
But what is in many ways the most interesting trilobite is a species of 
Orometopus, O. clatifrons, Ang., sp., of which the collections by Mr. Rhodes for 
H.M. Geological Survey and by Mr. Cobbold have furnished the entire form. 
Only the cranidium had hitherto been known, and this Brégger compared with 
Arethusina and Cyphaspis. But the characters of the complete form unmistak- 
ably place it in the Trinucleidz, though it is possessed of normal eyes. Moreover, 
being both more generalised and more primitive than the previously known 
members of this family, it indicates that the Trinucleide have been derived by 
specialisation and atrophy of the eye from more normal and eyed ancestors. 
Such degeneration is already anticipated in Orometopus, the eye of which is very 
small, consisting apparently of only sixteen facets. By its many points of agree- 
ment also with Harpes, it points to acommon origin for that family and the 
Trinucleidie, the atrophy of the eyes being, however, developed independently in 
each family. Indirectly it indicates also that other blind forms, such as Cono- 
coryphe, have been derived from normally eyed ancestors, 
The complete list of trilobites from the Shineton Shales known to the writer 
thus stands as follows :— 
