A CERA TA—MER O STOMA TA . 



401 



genal spines present; abdomen with eight segments besides the 

 very long, slender tail spine (telson) ; seventh and eighth segments 

 consolidated. Devonic-Carbonic. 



5. B. lacoei Packard. (Fig. 1699.) Carbonic. 



Genal spines parallel to median axis; pleura of abdomen of 

 nearly equal length. 



Coal Measures of Illinois. 



III. Prestwichia Woodward. 

 Differs from Belinurus in having seven abdominal segments, 

 all united, besides a short tail spine (telson). Carbonic. 



Fig. 1699. Belinurus lacoH^y^i. (Af- Fig. 1700. Prestwichia dance. (III. 

 ter Packard. ) Survey. ) 



6. P. danae M. and W. (Fig. 1700.) Carbonic. 

 Lateral angles of cephalothorax produced into long, slender 



spines; flattened border of abdomen with strong spines. 

 Coal Measures of Mazon Creek, Illinois. 



7. P. longispina Packard. Carbonic. 

 Median lobe of cephalic shield larger than in preceding, and eyes 



much nearer lateral margin; lateral spines much longer, extend- 

 mg nearly or quite to base of caudal spine. 

 Coal Measures of Pennsylvania. 



IV. Protolimulus Packard. 

 Cephalothorax large, with small appendages, its genal angles 

 less produced than in Belinurus; abdomen with six (seven? 

 26 



