CR USTA CEA—MALACOSTRA CA . 



379 



long, cylindrical, with an intricate hinge at the articulation with 

 the tail spines ; telson a long spine with a row of small spines on 

 each lateral edge. Cambric-Devonic. 



1 6. A. troyensis Ford. (Fig. 1682.) Cambric. 

 Oblique ; anterior end pointed ; posterior end rounded, produced, 



ventral margin grooved and reflected. 



Lower Cambric (Georgian) of Troy and Washington County, 

 New York. 



17. A. canadensis Whitfield. (Fig. 1680, ^, /.) Ordovicic. 

 Hinge line slightly less than greatest length, with strong, mar- 

 ginal rim, strong anterior node and several vertical grooves. 



Trenton of Ottawa region, Canada. 



VIII. Emmelezoe Jones and W. 



The two valves of the carapace elongate, narrow, and with dis- 

 tinct eye node; other nodes on cephalon wanting; surface with fine, 

 longitudinal raised striae. Siluric. 



18. E. decora Clarke. (Fig. 1683.) Siluric. 

 Carapace rather broad and bluntly pod-shaped ; hinge line straight 



for two thirds of shell ; ends vertical and rectangular; basal margin 



Fig. 1683. Emmelezoe decora^ a single valve and a nearly complete individual, but 

 with segments of abdomen reversed and thrown forward so as to project from anterior 

 end ; width of segments increased by compression, X 3- (After Clarke.) 



bluntly triangular; surface ridges sinuous and uniting; abdominal 

 segments of irregular length, longer and narrower posteriorly, 

 pustulose and longitudinally grooved on under surface. 

 Black Pittsford (Lower Salina) shales of New York. 



