54 A/exafu/er Petntnkevitch, 



Family Mazonidae. 

 A very little known family represented by one genus with one 

 species only. Middle eyes large, sitting on a tubercle close to anterior 

 edge of the cephalothorax. Post-abdomen, chelae, palpi and sternum 

 with coxae unknown. 



Genus Mazonia Meek and Worthen 1868. 



With the characters of the family. 



Genotype and only species M. woodiana M, and W. 



Mazonia ivoodiana Meek and Worthen. 

 Plate III, fig. 13. 



Mazonia woodiana Meek and Worthen, Geol. Surv. 111., 1868, 

 Vol. Ill, p. 653 with figure. 



The description of this unique specimen given by Meek and W'or- 

 then is sufficiently exact to be quoted here almost in full. But 

 their interpretation is at variance with mine, and I will therefore 

 add my views below. 



" The only specimen of the type of this proposed genus and species 

 yet known, is in a crushed condition, and of course shows but few of 

 its characters. Its cephalothorax is moderately convex, of a sub- 

 quadrangular form (its length being about 11.25 mm., and its breadth 

 10.5 mm.), with rounded anterior lateral margins, and the anterior 

 margin transversely truncated on each side of a small triangular 

 mesial projection. Its posterior lateral regions slope off abruptly 

 from an obscure ridge extending obliquely forward and outward, 

 from near the middle of the posterior margin, to a point near the 

 middle of each side, the sloping surface being marked by a few ver\- 

 minute irregularly scattering granules. From near the posterior 

 margin, a mesial furrow extends forward, widening and deepening 

 rapidly to the front, where it occupies one-third of the entire breadth, 

 and is partly filled by the ocuHferous prominence, which is the most 

 elevated part, and bears on each side a large eye. These mesial eyes 

 (the only ones known, or believed to exist) are circular, convex, about 

 1.75—2.00 mm. m diameter, and arranged for looking obliquely for- 

 ward, outward and upward. They are each surrounded by a ridge, 

 and so much elevated as to be seen almost entirely above the surface of 

 the cephalothorax on each side. No traces of lateral eyes can be seen 

 in the specimen, even by the aid of a magnifier, although the anterior 

 lateral margins (particularly on one side) are well preserved. 



