124 SUPPLEMENTARY APPENDIX. 



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, rctroflexed to fonn 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 furrows, 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 width." 

 T. agnosiifonnis. 



Remopleurides laticeps. 



Acidaspis bispinbsus. 



Sphffirexochus calvus. [Calymene clavifrons of 



Dalman.] 

 Encrinurus Stokesii. [Calymene variolaris of 



authors.] 

 Calymene arenosa. 



Calymene ? forcipata (a Lichas?). 



Portlockia sublaevis. 



Lichas laxata. 



Lichas pumila 



Ilomalonotus ophiocephalus. 



Otarion obtusum. 



Harpes ? megalops. 



Mr. M'Coy, in the same work, has placed the Balfiis tubercidafus of Kloden among the 

 Entomostraca, 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 fi'om 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 Aynostus {Batfus) tuheradotiis, 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 Agnosim. 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 Agnosius tuherculafus 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 



