TRILOBITES. 371 



the cephalic shield not extended in the posterior limb, nor the last segment of the thorax produced as in 

 the present form; while the pygidium is emarginate at the extremity, and dentate on the margin. 



While the glabella has the form of Olenus, and the general form of the cephalic shield corresponds to that 

 genus, the extension of the last segment of the body in spines parallel to the axis is a character of the 

 typical species of Paradoxides (see P. bohemiensis) : the pygidium is also much more nearly of the type 

 of Paradoxides, than of Olenus or Peltura. 



I propose therefore to designate this form by the generic name Bathynotus. 



GENUS BATHYNOTUS (n. g.) 

 [Gr. /Saflt/p, ampin*, and <WTOC, dormm ; in allusion to the ample central lobe or axis of the typical species.] 



General form elongate ovate, distinctly trilobate. Cephalic shield somewhat scmielliptical, with the 

 posterior angles prolonged in spiniform processes; posterior margin nearly straight across the center, and a 

 little concave at the sides ; anterior and lateral margins somewhat thickened. The facial suture (to judge 

 from the separated parts) is very simple, extending in a slightly -curving line from the front of the shield 

 backwards, and coming to the posterior margin within the limb. The glabella is prominent and well denned, 

 ovate in form and gradually narrowing towards the front ; the occipital furrow extends directly across the 

 glabella; the first pair of furrows above this are oblique and only slightly connected across the middle of the 

 glabella, while anterior to these are two slight indentations. Hypostoma subcircular, with the posterior end 

 a little wider. Eyes unknown. 



Thorax composed of eleven articulations; the axis broad and prominent, wider than the lateral lobes. 

 Lateral lobes nearly flat, narrow; the first five or six ribs short and narrow, inclining gently backwards; the 

 posterior ones becoming more abruptly bent and prolonged at the extremities, while the last pair are wider 

 and stronger, bent almost rectangularly, and produced in spiniform extensions much beyond the others. 



Pygidium distinct, semi-oval, the axis marked by several annulations, the lower part plain. Lateral 

 lobes plain or marked by ridges, and extending beyond the axis in a continuous flattened expansion. 



BATHYNOTUS HOLOPYGA.* 



This species is represented iipon Plate XIII, Fig. 3. There are but three distinct rings in the axis 

 of the pygidium, though there is a fourth indistinct depression, which may or may not indicate a fourth ring. 



The single species described in the last Report is illustrated in the accompanying figure. The specimen 

 is a mould or impression from which most of the crust has been removed, and we have the relief from a cast 

 made in this mould. The cheeks are separated and turned on one side; but in the drawing they are placed 

 in symmetrical relation with the other parts of the animal. The rings of the axis are marked 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 ninth 

 segment of the thorax; and in another 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 

 pygidium below has apparently 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 I conceive that there can be no hesitation in admitting the generic distinction of these fossils, 

 from those of any established genus of trilobites ; and however much, therefore, we may desire to avoid 

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



NOTE. I may remark, in this place, that the disposition of these three species does not include two 



* Olenus (FeJtura) holopyga; Twelfth Annual Report of the Regents of the University, on the State Cabinet of Natural History, p. 61. 



