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SUPPLEMENTARY APPENDIX.

Trinodus. New genus. Cephalic shield truncato-elliptical; glabella convex, nearlycylindrical, sharply defined ; cephalo-thoracic furrows, one on each side confluent with the nextfurrow, and with that defining the glabella, retroflexed to form a small flattened tubercle oneach side of the base of the glabella; neck segment small, narrow, convex, surrounding theglabella in front, the portion in front of the glabella as wide as that at the sides; cheekssurrounded by a thick, flattened, entire margin, of equal width all round; eyes none, facialsuture (? none); caudal shield equal, and similar in form to that of the head; axal lobesemicylindrical, very convex, divided by three segmental furrows, and having usually aprominent, lengthened tubercle extending down the middle, and which is not cut by the• segmental furrows; lateral lobes almost equal to the axal, very convex, not marked by thesegmental furrows; portion encircling the obtuse apex of the axal lobe about equal to thatof the sides, surrounded by a flattened margin, less than the side lobes in width.”T. agnosliformis.

Remopleurides laticeps.

Acidaspis bispinosus.

Sphaorexochus calvus. [Calymene clavifrons ofDalman.]

Encrinurus Stokesii. [Calymene variolaris ofauthors.]

Calymene arenosa.

Calymene ? forcipata (a Lichas?).Portlockia sublsevis.

Lichas laxata.

Lichas pumilaHomalonotus ophiocephalus.Otarion ohtusum.

Harpes ? megalops.

Mr. M c Coy, in the same work, has placed the Baltus tuherculatus of Kloden among theEntomostraca, in a genus which he names Beyrichia, and defines as follows :

“ Gen. Char. Shell bivalve, rotundato-quadrate, ventral margin slightly concave, endsvery nearly equal, obtusely rounded; sides equal, very gibbous, deeply impressed by a strongand wide sulcus, which extends from the ventral margin nearly to the dorsal, giving a bilobedor reniform appearance to each valve ; sulcus slightly nearer to the anterior end; within thissulcus on each valve, and close to the anterior (or smaller) side, is a lengthened ovaltubercle, nearly at right angles with the ventral margin, and reaching about two thirdsof the distance from thence to the dorsal margin ; surface smooth.

“ On first examining some specimens from the Irish Silurian sandstones, of what Iconsidered to be the Agnostus ( Battus) tuherculatus, Klod., of the Silurian System, I perceivedthat the vertical sulcus was very slightly nearer to one end than to the other, and that thelengthened tubercle forming the so-called mesial lobe was not precisely in the middle, asfigured and described by authors; this deviation, though very slight, was important, asshowing that we could not be really looking at the back of a symmetrical animal, as waspreviously supposed, and that the creature could not be an Agnostus. I also perceived thatsome of the specimens had the tubercle nearest the right, and others nearest the left end,and that consequently I had got the two valves of an entomostracous shell. I thereforedoubted the correctness of the reference to the English species until, on examining theoriginal specimens in London , I found that they too were unsymmetrical; I am now thereforecertain that my observations apply equally to the Irish fossil and the Agnostus tuherculatus ofWales , but should still have doubted the reference to Kloden’s Brandenburg species, had notan author well acquainted with the continental fossil published, a few T months ago, a Memoir,in which he incidentally alludes to this subject, and expresses an opinion of Kloden’s