When the imperfect fragments of a great Trilobite were discovered by myself in the Lingula-flags of St. David's, and brought before the Society in February 1863 (Quart. Journ. Geol. Soc. vol. xix. p. 275), I had no reason to suppose there was a chance of obtaining more specimens. The occurrence of so conspicuous and characteristic a genus as Paradoxides in our Primordial zone was, however, worthy of record, though the description was necessarily incomplete. But by the cooperation of Professor Griffiths, of Liverpool, and particularly the zealous examination of the beds by Mr. Henry Hicks, surgeon at St. David's, we are now in possession of much more abundant and perfect materials.