212 THE DEVONIAN OF MISSOURI. 



Description — "General form elliptical. Head semi-circular in outline, broadly con- 

 cave above, with the posterior angles curved and declining more abruptly. Glabella 

 somewhat pentagonal; length and greatest breadth nearly in the proportion of three to 

 four; very prominent in front, projecting beyond the rudimentary frontal limb, which 

 becomes more developed on each side, and below which is a defined groove, marking 

 the limits of the lower side of the cephalic test. Upper surface convex, gibbous in front, 

 having two pairs of transverse grooves, the middle and posterior ones of which are but 

 faintly defined; while the third or anterior ones, extending from the inner angle of the eye 

 backwards and a little inwards, are scarcely conspicuous, and, on many specimens, 

 not observable. First annular furrow strongly defined, and sometimes with a small tu- 

 bercle at the summit; first or intercalated annulation narrow and well defined, and 

 terminated at each extremity by a strong oblong tubercle, which is wider than the annula- 

 tion, and usually marked by two pustules at the summit, one on each side of the centre. 

 Occipital furrow wider and more strongly defined than the intercalated one, slightly 

 sinuous, and terminating in a deep cavity at each extremity; occipital annulation broad 

 and strong, slightly sinuate at the extremities, and, when entire, marked by one larger 

 central pustule and several smaller ones. Eyes of medium size, their summit less ele- 

 vated than the glabella, extending backwards to the line of the occipital furrow, com- 

 posed of seventeen vertical ranges of lenses; the entire number of lenses in full-grown 

 specimens about one hundred, and varying in the specimens examined from ninety-three 

 to one hundred and three. The axis of the thorax is prominent, and narrower than each 

 of the lateral lobes; the annulations furnished with a prominent node at each extremity. 

 The lateral lobes are flat or somewhat concave towards the axis, the articulations bend- 

 ing abruptly downward from the middle towards the extremities; each articulation 

 strongly grooved, the groove extending beyond the curvature. Pygidium semi-circular; 

 the axis prominent, with about nine annulations; the lateral lobes having about five or 

 six ribs, each with a groove along the centre. Sufrace of the glabella pustulose, and of the 

 articulations granulose, with some larger granules or pustules. The crust is thin, and the 

 interior of the glabella shows distinct cavities corresponding to the external pustules. 

 Hypostoma broad hastate; the buccal extremity obtuse, with a minute central point." — 

 Hall, 1859. 



Remarks — The incomplete cephalon observed departs from the foregoing descrip- 

 tion in that the eyes extend backward only to the line of the first annular furrow. As 

 shown by the portions preserved, the eyes originally had at least 15 vertical ranges 

 of lenses and an elevation of at least 6 ranges. The surface of the incomplete cephalon is 

 marked with subequal granules — visible to the naked eye. 



Dimensijns — Axial length about 11 mm., width 23 mm. 



