3Ionograph of the Crustacea of the Cincinnati Groiqr 123 



Found associated with Leperditia cylindrica at various elevations 

 about Cincinnati, but much less abundant. 



Leperditia Byrnesi — (S. A. Miller.) 



Fig. 10 — Leperditia Byrnesi Magnified view. 



Carapace minute, about :jJ-„th of an inch m length, width one third 

 less than length, greatest at the posterior third, with a straight cardinal 

 margin or hinge line nearly the length of the shell. Valves moder- 

 ately convex. Tubercle at the anterior end, near the dorsal margin, 

 obtuse and apparently directed posteriorly, with a depression or sulcus 

 reaching to the dorsal margin, at the base of the tubercle on the poster- 

 ior side. Tubercle or spine on the posterior third, near the dorsal mar- 

 gin, rising to an acute point, higher than the anterior tubercle, and pro- 

 jecting to or beyond the dorsal margin. There is a corresponding 

 internal pit for each tubercle and mesial elevation between them. 

 Surface smooth. 



The specific name is given in honor of Dr. E. M. Byrnes, of Cincin- 

 nati, an ardent student of natural history, active member of the Cin- 

 nati Society of Natural History, and indefatigable collector of fossils, 

 shells and minerals. 



This species is found within a range of from 7 to 14 feet above low 

 water-mark, under the bank of the Ohio River in the First Ward of 

 Cincinnati. I^ot observed elsewhere, but this may be owing to the 

 fact that it is so small as to be scarcely visible to the naked eye. 



Third Family Trilobitadce. 



Body covered (with a few exceptions) by a longitudinally trilobed 

 crust, the head and abdominal segment anchylosed into distinct ce- 

 phalic and caudal shields, the thoracic segments alone remaining dis- 

 tinct and movable. 



The cephalic shield is approximately semi-circular ; when most fully 

 developed it presents the following parts : An external, thickened 

 "limb" or '•'margin," often prolonged backward at the lateral angles into 

 "ivings;" the shield is visually divided into two i^ieces by a suture pe. 

 culiar to trilobites, termed the "eye line" or "facial suture," being con- 

 tinuous from one side to the other near the front margin, descending 



