50 A Contribution to the Lower Devonian Faunas of Maryland 



Description. — " General form elliptical. Head semicircular in outline, 

 broadly concave 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, project- 

 ing 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 wath a small tubercle 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 auuulations, and usually marked by two pustules at the summit, 

 one on each side of the center. Occipital furrow wider and more strongly 

 defined than in 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 elevated tlian the glabella, ex- 

 tending backwards to the line of the occipital furrow, composed of seven- 

 teen 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 fiat or sonle^vhat concave towards the 

 axis, the articulations bending abruptly downwards from the middle 

 towards the extremities : each articulation strongly grooved, the groove 

 extending beyond the curvature. Pygidium semicircular ; the axis promi- 

 nent, with about nine annulations; the lateral lol)es having about five or 

 six ribs, each with a groove along the center. Surface of the glabella 

 pustulose, and of the articulations granulose, with some larger granules or 



