No. 89,] 119 



by a row of ■small spines. The great length of the spines or processes, from the 

 posterior angles of the cephalic shield, is a remarkable feature : in this individual, 

 their extremities must have reached as far as the eighth or nmth segment of the 

 thorax; and in ar.other individual, these separated parts have similar proportions. 



In one imperfect specimen of this species, with narrower axis, we have eleven 

 body rings, including the elongated posterior one; but behind this there are three 

 annulations of the axis, the two anterior of which have somewhat the appearance 

 of free segments, and are likewise marked upon the lateral lobes; while the py- 

 gidiura below has apparentl}^ a single annulation, extending into the lateral lobe. 



This one appears to be specifically distinct from the preceding, in its narrower 

 axis : nevertheless this feature may be due to distortion, as also some other points 

 of apparent difference. 



It is to be regretted that the materials at my disposal are so imperfect as to leave 

 some points yet in doubt; but T conceive that there can be no hesitation in admit- 

 ting the generic distinction of these fossils, from those of any established genus of 

 Trilobiths; and however much, therefore, we may desire to avoid^he multiplica- 

 tion of genera, it seems to be unavoidable in the present instance. 



The geological horizon of the shales in which these trilobites occur having been 

 made a matter of discussion among geologists, I shall refer those interested in the 

 subject to the forthcoming Report upon the Geology of the State of Vermont by 

 Prof E. Hitchcock. 



NoTK. I may remark, in tbis place, that the disposition of these three species does not in- 

 clude t'.vo which I have designated as Olexus in the first volume of the Palgeontology of Now- 

 York ( pa. 266 - 268, pi. 67, f. 2, 3). One, the O. asaphoides, showing six of the lateral ribs 

 of the thorax, has no ribs larger or longer than the others, though the form of the cephalic 

 shield and the glabella are very similar to Barrandia : in that one there are four pairs cf 

 glabellar furrows, the two posterior ones of which are slightly indented a,cross the ■centre of the 

 glabella. The eyes are elongated, and more curved than in Barrandia thompsonl. We have, 

 therefore, yet other undetermined material in these slates. 



NEW SPECIES OF FOSSILS FROM THE IIUDSON-RIVER GROUP OF 

 OHIO, AND OTHlilR WESTERN l^iTATES. 



CALYMENE CHRISTYI ( n.s.). 



General form elongate ovate, symmetrical : body gibbous, the p3'gidium equalling 

 the length of the head. Head semicircular, the frontal border expanded, and 

 gradully narrowing on the sides; the posterior angles terminating in a short 

 sharp spine. Glabella wide, slightly narrowing towards the front, regularly 

 convex, strongh' defined by the dorsal furrows, a little concave in the middle of 

 the base : occipital furrow well defined, nearly straight, and in right line with 

 the cheek furrows; post<3rior furrow oblique, defined but not deep; the middle 

 one nearly rectangular to the axis, while the anterior one is but slightly indented. 

 The posterior lobe is.Tr.uch wider than the middle one, and about the same width 

 as the anterior one. Cheeks small. Eyes very prominent. 



Thorax with thirteen segments; the axis salient, and a little wider in the middle 

 than the lateral lobes; the articulations of the latter flat, or slightly curving for 

 a little more than one-third their length, when they are suddenly bent doAvn- 

 wards. 



The PTGiDiUM is gibbous, semielliptical, with the axis very prominent and marked 

 by seven or eight rings, the last one being longer and more prominent, with a 

 minute scarcely defined node at the extremity : lateral lobes marked by six 

 flattened ribs, the last one of which is minute, the expansion being continued ia 

 a narrow flattened border around the posterior extremity. 



