1887.] NATURAL SCIENCES OF PHILADELPHIA. 15 



course of the facial suture lines fully correspond with them, but 

 they differ by the much smaller size of their pygidia in compari- 

 son with the size of the concerned thoracic divisions and the 

 heads. A fiirther difference is in the number of thoracic segments, 

 which in them is nine instead of eight, and seven, as in the two 

 first described typical forms of Ogygla. 



The glabella of the latter also shows three lateral furrows, while 

 in the two forms to be described, four very well marked glabellar 

 furrows are observable. 



These differences and principally the difference in the proportion 

 of the size of head, thorax and pygidium, appear to me sufficient 

 to distinguish these forms from the genus Ogygla, and I propose 

 to apply to them the generic name EmboUmus. 



Embolimus spinosa, nov. sp. PI. I, fig. 3. 



Only one, almost perfect specimen of this form is in the collec- 

 tion, but the number of fragmental specimens observable in the 

 slabs prove that this is not a rare sj^ecies. 



The specimen figured is 34 millimetres long ; length of head 14 

 millimetres; length of thorax 15 millimetres; length of pygidium 

 5 millimetres, without counting the length of spinous processes. 



The glabella is large, moderately convex, of equal width in all 

 its length, reaching close to the front margin, which is formed by 

 a narrow upturned rim. 



The four glabellar furrows are well developed, none reaches the 

 centre of the glabella, the hinder ones are the largest, running 

 obliquely backward, the second and third furrows extend almost 

 at right angles from the margin of the glabella, but the apex of 

 the second is turned backward while the apex of the third furrow 

 is curved forward. The fourth and smallest furrow is directed 

 obliquely forward. 



The occipital ring forms a triangular projection of the posterior 

 margin, which is crowned with a stout short spine, also each of 

 the thoracic annuli exhibits a faint indication of former orna- 

 mentation by a spine which is broken off in the si^ecimen. 



The pygidium has four sharp annulations with as many costal 

 appendages, which, a short distance off from the rachis, are ab- 

 ruj^tly bent backward, tapering into long spines projecting over 

 the pygidial margin in a direction parallel with the longitudinal 

 axis of the body. 



