14 PROCEEDINGS OF THE ACADEMY OF [1887. 



figured specimen is seven centimetres long, and five centimetres 

 wide, measuring from one genal spine to the other. 



Head, thorax, and pygidium of equal length. 



General form of the head and course of the facial sutures cor- 

 respond almost completely with the previously described species. 

 The glabella of this form is somewhat broader and more j)romi- 

 nent than in the former ; also the glabellar furrows are more 

 distinctly marked ; they are three in number, the hinder one is 

 the largest, directed obliquely inward and backward, but not 

 reaching to the centre of the glabella. 



The palpebral rim and the rugosity continued from it upward 

 across the fixed cheeks are the same as in the former sjiecies. 



The movable cheeks are protracted into long slender sj^ines, 

 which reach as far down as the fifth thoracic rib. 



Rachis broad, almost equal in diameter with the length of the 

 corresponding ribs, deducting their spiniform prolongations. 

 The occipital ring terminates with a triangular monticulose prom- 

 inence, overlapping the first thoracic ring, and likewise each one 

 of all these annuli of the thorax, and the pygidium bears a 

 strong spine on the median line. 



The thorax of this species is, in all the specimens examined, 

 composed of only seven segments. 



The pygidium has five aunulations with as many ribs corre- 

 sjDonding to them. These ribs dilate considerably toward the 

 margin, as in the former ; but while in that, a smooth rounded rim 

 edges the pygidium, in this form the j^rincipal ruga of each rib 

 extends beyond the margin of the pygidium under the form of a 

 strong acute spine, directed backward, so as to be almost parallel 

 with the axis of the body. Five of such spines fringe each side 

 of the pygidium ; their size is gradually diminished toward the 

 posterior end. 



The hyj)ostoma is in most of the specimens preserved, occupy- 

 ing its natural position. The shape is represented by one of the 

 annexed figures and needs therefore no further verbal description- 

 Many loose, but much smaller hypostomas, of Avhich I likewise 

 figure a few (PI. I, figs. 26 and 2c), were found scattered through 

 the slate rock ; to which of the associated trilobitic forms they 

 belong, I was unable to ascertain. 



Two other forms of Trilobites occur with the just described 

 Ogygias, which in the configuration of their heads and in the 



