CRUSTACEA. 1G9 



Post-abdomun. Caudal plate short, sub-quadrangular upon the ventral side, and 

 sharply elevated on the anterior edge; sub-pentagonal on the dorsal side, 

 elevated in the middle on the posterior half, and produced into a telson 

 which is usually about twice as long as the last somite. Articulated to 

 the caudal plate are two lateral spines or cercopods, each longer than the 

 telson. Each of the three spines is elevated or carinated upon the dorsal 

 surface, the telson grooved along the sides, and the cercopods grooved upon 

 the ventral surface. 



Surface of the abdomen and caudal spines smooth or finely granulose. 



Dimensions. Although specimens of Echinocaris punctata are not uncommon 

 at certain localities, the parts are usually disjointed and entire individuals are 

 extremely rare. The most complete specimen observed (pi. xxviii, fig. 3), 

 is of average dimensions and measures as follows : 



Length 



Width 



The somites of the abdomen in this specimen have the following lengths : 

 First, 4 mm.; second, 4.5 mm.; third, 5 mm. ; fourth, 6 mm. ; fifth, 6.5 mm. ; 

 sixth, 9 mm. The largest individual observed in which the parts are in 

 conjunction affords the following measurement : 



Body. Cephalothorax. Abdomen. Post-abdomen. 



Length 195 mm. 68 mm. 96 mm. 39 mm. 



Width 88 mm. 44 mm. 



A single very large carapace has a length of 90 mm., and the individual to 

 which it belonged must have been about 244 mm. or nearly 10 inches in 

 length when entire. 



Observations. Specific Diagnosis. The specimen from which the original 

 description of Ceratiocaris ? punctatus, Hall (loc. cit.), was drawn, is a large 

 carapace, represented both in the figure given in the Sixteenth Report of 

 the State Museum, and also in the Illustrations of the Devonian Fossils, with 

 a strong node at the posterior extremity of the dorsal line. This node proves 



