The organization of Trilobites, deduced from their living affinities. With a systematic review of the species hitherto described / By Hermann Burmeister ... Ed. from the German by Professor Bell ... and Professor E. Forbes.

  • Burmeister, Hermann, 1807-1892. Organisation der Trilobiten. English
Date:
1846
Catalogue details

Licence: Public Domain Mark

Credit: The organization of Trilobites, deduced from their living affinities. With a systematic review of the species hitherto described / By Hermann Burmeister ... Ed. from the German by Professor Bell ... and Professor E. Forbes. Source: Wellcome Collection.

    140/168 (page 124)
    Trinodus. New genus. Cephalic shield truncato-elliptical; glabella convex, nearly cylindrical, sharply defined ; cephalo-thoracic furrows, one on each side confluent with the next furrow, and with that defining the glabella, retroflexed to form a small flattened tubercle on each side of the base of the glabella; neck segment small, narrow, convex, surrounding the glabella in front, the portion in front of the glabella as wide as that at the sides; cheeks surrounded by a thick, flattened, entire margin, of equal width all round; eyes none, facial suture (? none); caudal shield equal, and similar in form to that of the head; axal lobe semicylindrical, very convex, divided by three segmental furrow7s, and having usually a prominent, 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 the segmental furrows; portion encircling the obtuse apex of the axal lobe about equal to that of the sides, surrounded by a flattened margin, less than the side lobes in wfidth.” T. agnostiformis. Remopleurides laticeps. Acidaspis bispinosus. Sphserexochus calvus. [Calymene clavifrons of Dalman.] Encrinurus Stokesii. [Calymene variolaris of authors.] Calymene arenosa. Calymene ? forcipata (a Lichas?). Portlockia sublaevis. Lichas laxata. Lichas pumila Homalonotus ophiocephalus. Otarion obtusum. Harpes ? megalops. Mr. McCoy, in the same work, has placed the Baltics tuberculatus of Kloden among the Bntomostraca, in a genus which he names Beyrichia, and defines as follows : “Gen. Char. Shell bivalve, rotundato-quadrate, ventral margin slightly concave, ends very nearly equal, obtusely rounded; sides equal, very gibbous, deeply impressed by a strong and wide sulcus, which extends from the ventral margin nearly to the dorsal, giving a bilobed or reniform appearance to each valve ; sulcus slightly nearer to the anterior end ; within this sulcus on each valve, and close to the anterior (or smaller) side, is a lengthened oval tubercle, nearly at right angles with the ventral margin, and reaching about two thirds of the distance from thence to the dorsal margin ; surface smooth. “ On first examining some specimens from the Irish Silurian sandstones, of what I considered to be the Agnostus (Battles) tuberculatus, Klod., of the Silurian System, I perceived that the vertical sulcus was very slightly nearer to one end than to the other, and that the lengthened tubercle forming the so-called mesial lobe was not precisely in the middle, as figured and described by authors; this deviation, though very slight, was important, as showing that we could not be really looking at the back of a symmetrical animal, as was previously supposed, and that the creature could not be an Agnostus. I also perceived that some 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 therefore doubted the correctness of the reference to the English species until, on examining the original specimens in London, I found that they too were unsymmetrical; I am now therefore certain that my observations apply equally to the Irish fossil and the Agnostus tuberculatus of Wales, but should still have doubted the reference to Kloden’s Brandenburg species, had not an author well acquainted with the continental fossil published, a few months ago, a Memoir, in which he incidentally alludes to this subject, and expresses an opinion of Kloden’s