370 PROF. HALL'S DESCRIPTION. 



The facial suture can be traced a little forward of the eye, but its direction on the anterior margin has 

 not been ascertained; on the posterior margin, its direction is shown as accurately as it can be from crushed 

 and distorted specimens. The body, or thorax and pygidium, is drawn essentially from a single individual. 

 The line just within the free extremities of the pleura is shown in this and other specimens, and indicates 

 the limits of the crust on the lower side. The caudal shield shows no more than the axis which is prolonged 

 into a slender pointed spine, strengthened by a sharp elevated ridge beginning near the anterior margin, 

 and extending to the extremity. 



The entire absence, so far as can be seen, of lateral lobes of the pygidium, is a marked feature; and this 

 especially is in strong distinction with Olenus. 



BAKRANDIA VERMONTANA.* 



The accompanying figure of B. vermontana (Plate III, Fig. 5) illustrates also the character of the 

 cephalic shield, and the greater strength and extension of the third articulation of the thorax. The frag- 

 ment of thorax and pygidium, heretofore referred to this species (Twelfth Annual Report of the Regents), 

 prove, on further examination, to be parts of the following or a similar species there referred to Peltura. 



General form elongate; the posterior extremity obtuse. Head semioval, twice as wide as long, the 

 posterior angles produced in short acute spines. Eyes narrow elongate; the space from the center of the 

 head to the outer margin of the eye much greater than the cheek, and the distance from the anterior angle 

 of the eye to the frontal margin less than the length of the eye. Glabella lobed; hypostoma broad oval. 



Thorax imperfect, preserving six articulations and part of the seventh; the middle lobe wider than the 

 lateral ones. The third articulation is much broader towards and at its lateral margin, and is prolonged 

 obliquely downwards in a sharp spine, which reaches below the seventh articulation; the lateral extremi- 

 ties of the other articulations produced in short acute spines. 



Another fragment, which is apparently of the same species, preserves eleven articulations of the thorax 

 and the pygidium. The upper articulations are imperfect at their extremities; the last one is bent abruptly 

 downwards, and terminates in a long spine on each side reaching below the pygidium. Pygidium semioval; 

 the axis marked by four annulations, the two upper of which are faintly indicated in the lateral lobes. 



This species differs from the preceding in its proportionally narrower form, the relative proportions of the 

 parts of the head, and the short acute posterior spines. The comparative width of the middle and lateral 

 lobes of the thorax is a very distinguishing feature. 



[NOTE BY c. H. H. Plate XIII, Fig. 4, shows an outline of a more perfect specimen than any to which 

 Prof. Hall had access. Plate XIII, Fig. 2, is a copy of the drawing made by Prof. Hall. Fig. V, on the 

 same plate shows all the segments of the animal below the third articulation, although part of them are 

 separated from the rest.] 



In my examinations of these Trilobites, continues Prof. Hall, I had hoped to unite the three forms here- 

 tofore described, under a single genus ; but on more careful comparisons, I find that the one before referred 

 to Peltura is so dissimilar, that I am unable, by any proper extension of the generic characters ofSarrandia, 

 to include it in the same genus. In the specimens which appear to possess the thorax and pygidium entire, 

 there are but eleven thoracic segments; the third segment is not enlarged and produced as in Barrandia, but, 

 on the other hand, the anterior segments, to the number of five or six, are little prolonged at their extremi- 

 ties ; the prolongation increases in the posterior segments, while the last one of the thorax is enlarged as it 

 recedes from the axis, and at its broadest part makes an abrupt geniculation, turning almost rectangularly 

 backwards, is prolonged into sharp spines in a direction parallel to the axis and extending beyond the 

 pygidium. The axis of the pygidium is marked by three rings, while the lateral lobes are apparently 

 smooth (in one specimen), and the entire form is semielliptical, the axis obtuse at its posterior extremity, 

 and bordered by a smooth extension of the crust from the lateral lobes; which is in strong contrast with the 

 preceding genus. Nor can it be properly placed under Peltura, which has twelve segments of the thorax, 



* This and the preceding species were published as Oleitus thompsoni and 0. rermonlana, in the Twelfth Annual Report of the Regents 

 of the University on the State Cabinet of Natural History, pp. 66 and 60. 



