TEILOBITES. 369 



The smaller number of thoracic segments is a distinguishing feature, and the direction of the segment 

 furrow differs essentially. In one feature, that of the greater development of the third segment, it corres- 

 ponds with Paradoxides, where the second segment has a greater development than the others. In the 

 extreme development of the posterior segments, in one species, there is likewise a similarity with Paradox- 

 ides. In the slight development of the pygidium, our fossil corresponds in some degree with Paradoxides. 



In the perfect condition, one species appears to have been furnished with a row of nodes or spines along 

 the dorsal ridge. 



We have, therefore, although the material is imperfect, the means of showing well-marked distinctions 

 between these forms and the allied genera Olenus and Paradoxides. 



The species referred to Peltura has the cheeks separated, and therefore there is some obscurity about the 

 suture margins. The expansion of the lateral lobes of the thorax is imperfect in the specimen figured; 

 but, from examination of this and other specimens, the third segment does not appear to have been pro- 

 longed as in the two others. The pygidium has four or five rings on the axis, and the lateral lobes are 

 expanded and the extremity rounded; moreover I am able to count but eleven articulations in the thorax : 

 these, with other characters enumerated, seem to exclude it from generic association with the two species 

 referred to Olenus. For these, excluding the one referred to Peltura, I would propose the generic designa- 

 tion Barrandia. 



GENUS BARRANDIA, (n. g.) 



" General form broadly ovate or elongate ovate, distinctly trilobate. Cephalic shield broad, somewhat 

 semicircular; the width more or less than twice the length, with the posterior angles projecting in long 

 spiniform points; the posterior margin is nearly straight or slightly concave, with a slight sinuosity at the 

 outer angle just within the cephalic limb; the anterior and lateral margins have a thickened or elevated 

 border, within which is a well marked groove or depression of the crust. The glabella is well pronounced, 

 of nearly equal width throughout, or slightly narrowing and rounded in front; marked by three pairs 

 of furrows (perhaps from two to four), the posterior one of which is nearly or quite continuous across from 

 the posterior angles of the eyes. The facial suture has not been fully determined, but appears to extend 

 in a curving line from the front margin to the interior angle of the eye, and from the posterior angle of the 

 eye it turns abruptly outwards towards the postus-lateral angle of the cephalic shield. 



Eyes large and well developed, elongate semilunate, extending from near the base of the shield more than 

 half way to the anterior margin. Hypostoma broadly ovate, little longer than wide. 



Thorax composed of thirteen or fourteen articulations ; the axis being moderately convex, and usually 

 much narrower than the lateral lobes (and sometimes apparently marked by a row of nodes or short spines 

 along the summit.) Lateral lobes nearly flat; the ribs, to about the eighth or ninth, extending almost 

 rectangularly, or slightly inclined from the axis for one-third to one-half their length, where they are bent 

 abruptly backwards. The third segment is stronger, and much more prolonged than the others. The last 

 segments of the lateral lobes are produced directly backwards, or sometimes a little convergent below. 

 The segments of the lateral lobes are marked by a broad longitudinal furrow, nearly parallel to the anterior 

 margin; leaving an abruptly elevated ridge or border upon that side as far as the geniculation of the 

 segment, where the groove runs along the center, dying out on the recurved extremities. 



Pygidium distinct, narrow, elongated, the axis narrow, and acutely pointed ; without rings ? Lateral 

 lobes narrow or obsolete, and free from transverse ridges or furrows. 



The accompanying figure (Plate XIII, Fig. 1), illustrating this genus, combines characters observed in 

 several imperfect specimens of the same species. The form of the cephalic shield is shown in two or three 

 individuals ; the glabella is crushed in all the specimens examined ; but the form is made out as nearly as 

 possible, from the materials in our possession, and cannot vary much from the truth. There are three pairs 

 of glabella furrows anterior to the occipital furrow. In the area between the extremities of the glabella 

 lobes and the eyes, there are on each side, in the species figured, two low oblong tubercles; but I cannot be 

 sure that these are of generic importance, and it might be supposed possible that this appearance is due to 

 the crushing of a prominent part of the crust, were it not that the feature is symmetrical and correspondent 

 on the two sides. 



