964 THE AMERICAN NATURALIST.  [Vou. XXXIII. 
5I 
ea 
va 
ae 
Anterior portion of carapace a very little more than twice as long as 
anterior portion . $ . C. spinosus Bun. 
Anterior portion of carapace not more in twice as long as posterior 
portion : : Zia 
Rostrum faintly carinate . : : ; > ; c ; Pieces F ax. 
Rostrum not carinate . ; : i ; $ : ‘ . §3 
Acumen of moderate length . : : : . C. hylas Fax. 
Acumen long and slender ; : ; : . C. putnami Fax. 
Sides of rostrum concave . : ‘ i ; : : 55 
Sides of rostrum not concave . è : i - ‘ 
Lateral spines of carapace strong . ; C. indianensis Hay 
Lateral spines of carapace small or obivlete , : 
Postorbital spines well developed . : ; . C. harrisoni Fax. 
Postorbital spines small or obsolete ; ta Ce RCE EGE, 
Lateral spines of carapace strong . ; ; ‘ Re 
Lateral spines of carapace small and wak . 60 
Sides of rostrum nearly parallel, acumen long ann eather slender 1 O 
Sides of rostrum convergent, acumen short . ; . C: kayi Fax. 
Postorbital spines strong, sides spiny . : : C. affints Say. 
Postorbital spines small, sides not spiny . . C. erichsonianus Fax. 
Proximal segment of telson with three or four spines on each side 
C. fallax Hag. 
Proximal segment of telson with only two spines on each side . -6r 
Rostrum deeply excavated. . propinguus sanbornii Fax. 
Rostrum slightly excavated or gabplade ; ; ; ; ; . 62 
Tip of acumen abruptly turned upward . : ; C. virtlis Hag. 
Tip of acumen gently curved upward Ž . . C, obscurus Hag. 
Carapace with one spine on each side just behind cervical groove . 64 
Carapace without lateral spines ; ; . 67 
Postorbital and branchiostegal spines ae daveliped : ; . 65 
Postorbital and Wir: spines small or wanting . i . 66 
Areola narrow ; : . C. wiegmanni Erich. 
Areola broad . : : : C. acuminatus Fax. 
Base of rostrum slightly tor eolate . ‘ > . C. immunis Hag. 
Base of rostrum not foveolate . ; : : «o C, uirilis Hag, 
Branchiostegal spine developed 
Branchiostegal spine wanting . a 
Anterior border of carapace decidedly airlines below the eye . 69 
Anterior border of carapace hardly angulated : . 73 
Proximal segment of telson with three or four spines on sich side - 70 
Proximal segment of telson with only two spines on each side cyi 
Rostrum pubescent and nearly flat above ‘ C. mexicanus Erich. 
Rostrum not pubescent, deeply excavated : ‘ C. alleni Fax. 
Inner surface of hands with a more or less thick covering of soft setæ 
C. barbatus Fax. 
