No. 396.] NORTH-AMERICAN INVERTEBRATES. 965 
71 Inner surface of hands not setose 
: i 7 ý j rg 
72 Cervical groove broken on the sides 3 ; : C. virilis Hag. 
72 Cervical groove not broken on the sides . ; C. latimanus Erich. 
73 Areola carinate ; ; : ‘ F . C. stmulans Fax. 
73 Areola not carinate ; i 3 ; : 4 ; . 83 
T A of Papa affinis 6 showing most of the structures mentioned in the diag- 
f the specie crayfishes, a, chela; 4, rst antenna (antennules); c, 2d antenna 
na); d, ictal oa chelaped); e, antennal scale; _/, acumen (of rostrum); g, meros 
ba wpe A, rostrum ; 7, suborbital angle; 4, postorbital spine and ridge; Z, anterior 
(gastric) portion of carapace; s, lateral spine (of carapace); %, second pair of legs ; 
o, DRA groove; 4, third pair of ad ae ; g, areola; 7, posterior (branchio-cardiac) portion 
of carapace; s, ¢, x, v, w, x, segments of abdomen; y, z, outer and inner blades of caudal 
fin; Zz, @, proatinal and distal segments of telson. 
74 Rostrum with a longitudinal median carina above . C. medius Fax. 
74 Rostrum not carinate . o; : : : ‘ ae 
75 Rostrum deeply excavated . : ; . : i A . 76 
75 Rostrum not deeply excavated : : ; i : oF 
76 Rostrum strongly decurved, areola narrow : ‘ C. dubius Fax. 
