When I first drew attention to this genus at the Bath Meeting of the British Association in 1864, only one nearly perfect specimen was known. Mr. Salter was acquainted with this form, so long ago as 1857, and referred to it, among other new and undescribed Crustacea, in a paper “On some New Palæozoic Star-fishes” found at Leintwardine, Shropshire, under the name of Limuloides. Portions of several others had also been met with, to which Mr. Salter attached MS. names in (the Museum of Practical Geology, Jermyn-street, but they have not been heretofore described. The most perfect of these Limuloid forms was described by me in a paper read before the Geological Society in June, 1865.3 (See Plate X. Fig. 1.)

In a former communication I stated that the line of division between the Skiddaw Slates and the overlying Volcanic series (Green Slates and Porphyries), in the neighbourhood of Keswick, was a faulted one, and not an unconformity, as supposed by Mr. Dakyns. I added that the evidence of an unconformity (if there was one), between these two series of beds, must be sought for elsewhere than in the district described by Mr. Dakyns. Since then I have examined many miles of boundary between these formations, and have as yet only seen one unfaulted junction, and this is near Bootle, in the Black Combe district, Cumberland; but this section at once sets at rest the question of unconformity or conformity. Not only do the Volcanic series lie at the same inclination with the Skiddaw Slates below them, but beds of the latter alternate with beds of the former, showing a perfect sequence and conformity. When the whole of the boundaries between the Skiddaw Slates and Volcanic series are traced, there may be found other spots also showing conformity and passage.

The genera named in the title constitute in our opinion a new I family belonging to the helictobrachial section of the class Palliobranchiata or Brachiopoda. We propose to designate it Trimerellidœ, after the type genus.

Having recently had the opportunity of carefully investigating the genus Tentaculites, I was led to the conclusion that several fossils of diverse zoological affinities had been included under this head, and that the prevalent differences of opinion as to the systematic position of this genus might be thus readily explained (American Journ. of Science and Arts, vol. iii., no. 15, 1872). Originally founded by Schlotheim in 1820 (Petrefact. i., p. 377), Tentaculites, as its name implies, was believed to comprise fossils which were nothing more than the slender terminations of the jointed arms of Crinoids. Modern palæontologists have been divided in opinion as to whether Tentaculites was truly referable to the Tubicolar Annelides or the oceanic group of the Pteropoda— most recent authorities placing the genus in the latter class. In point of fact the difficulty has really arisen from the circumstance that two dissimilar sets of fossils have actually been included under Tentaculites; some of these being genuine Pteropods, whilst others are equally genuine Tubicolar Annelides. As all the typical species belong to the first group, it follows that the genus Tentaculites remains a Pteropodous one; whilst the Annelidan forms must be referred to new genera.

Somewhat further to the west of Karsok, and about 50 feet higher up, occurs another similar stratum, containing a mass of graphite, so soft that it may be cut with a knife. This spot was not, however, accurately examined. A similar stratum of graphite imbedded in sand and clay occurs also at a very great height above the sea at Niakornet, but time did not admit of our visiting that spot.