NOTICE TO COEEESPONDENTS. 



In our next part it would be iii some respects advisable to go on with the highest 

 and most compact group of the smooth-eyed Trilobites (see p. 2), viz. the Proefida, 

 which comprise the Carboniferous species ; but though materials are abundant, they are 

 not complete, and the specimens are much scattered ; I shall therefore, in Part V, after 

 the Bronteidce are finished, proceed Avith the lower groups, viz. — 



jUglinid-E — given at p. 124 as a subgroup of the AsaphidcB, but possibly distinct, and 



certainly much lower than the others. 

 TRiNUCLEiD.i; — for which materials are in plenty. 

 AGXOSTiD.t — now of many species. 



With these we shall close the First Volume. 



In Vol. II it is proposed to follow the left-hand column (p. 2), through the "pri- 

 mordial " genera of the Olenida; and Conocephalida, which are already numerous, and will 

 be still better known by that time ; then to take up the more aberrant groups — Lichada, 

 AcidasjAda, Haiyedidce, &c. This will lead us to the Cyphaspidce, before describing the 

 Proetida : and there is an intimate relation between the two last-named groups, in spite 

 of the numerous free body-rings which characterize the one, but which are soldered into 

 a large post-abdomen or tail-piece in the highest and terminal forms of the Proetida, — 

 viz. : the Carboniferous species of Phillipsia, &c. 



I beg to thank our numerous friends for their ready help. Many additional species 

 of the groups already passed in review have, of course, turned up ; but these will best 

 appear in the Appendix to Vol. II, should health and leisure be granted me to complete 

 the work. If not, I shall have indicated, I hope, the right path for my successor. 



Our friends, therefore, will please to communicate all their best specimens (with strict 

 localities) of the three groups above mentioned. They may be left at the Geological 

 Society ; or forwarded to me at 45, Great Russell Street, or to — 



8, Bolton Road, St. John's Wood, London. 

 April 29th, 18G7. 



J. . Saltlk. 



