86 
THE VOYAGE OF H.M.S. CHALLENGER, 
(1) Spines of rostrum distinct, acute. Palms of ckelipedes with or without 
spines on the superior margin. 
a. Palms of chelipedes in the adult with spines on the upper margin. 
Mithrax spinosissimus (Lamarck). Florida, West Indies (to 
100 fathoms). 
Mithrax cornutus (Saussure). West Indies ; Florida Straits (to 
589 fathoms) ; Bahia. (Specimens taken by Captain E. Cole, 
46 miles south of Key- West, Florida, are in the British 
Museum Collection). 
Mithrax aculeatus (Herbst). West Indies ; Yera Cruz. 1 
b. Palms of chelipedes without spines. 
. Mithrax acuticornis, Stimpson. Near the Quicksands and 
Tortugas, to 42 fathoms (perhaps, as noted by A. Milne 
Edwards, the young of Mithrax cornutus). 
Mithrax holderi, Stimpson. Tortugas. 
Mithrax armatus, Saussure. West coast of America ; Mazatlan. 
Mithrax rostratus, Bell. ? 
Mithrax ursus, Bell ( = Mithrax belli, Gerstsecker, nec Cancer 
ursus, Herbst). Galapagos Islands ; Chili (Brit. Mus.). 
(2) Spines of rostrum short, tuberculiform or obsolete. Chelipedes with the 
palms unarmed. 
Mithrax hispidus (Herbst) = Mithrax pleur acanthus, Stimpson, 
var. South Carolina ; Florida Straits ; West Indies (to 125 
fathoms) ; Yucatan Channel, near the Jolbos Islands ; Brazil 
(30 to 350 fathoms). 
Mithrax Isevimanus, Desbonne and Schramm. Guadeloupe. 
Mithrax tuber culatus, Stimpson. California ; Mazatlan. 
Mithrax depressus , A. Milne Edwards. Guadeloupe ; Woman 
Key. 
Mithrax leucomelas, Desbonne and Schramm. Guadeloupe. 
Mithrax verrucosus, Milne Edwards. West Indies. 
Mithrax pygmseus, Bell. Panama (10 fathoms). 
Mithrax triangulatus , Lockington. Gulf of California. 
2. Carapace very much depressed, with smooth, shallow interspaces or sulci between 
the tubercles of the dorsal surface of the branchial regions ; the lateral margins tuber- 
1 Mithrax trispvnosus, Kingsley ( Proc . Boston Soc. Nat. Hist., vol. xx. p. 148, 1879), from Florida, has three acces- 
sory spines on each spine of the rostrum. It is not stated whether the palms of the chelipedes are spinuliferous ; 
they are referred to as “naked.” I have observed more or less distinct indications of accessory rostral spinules in 
Mithrax spinosissimus and Mithrax aculeatus. 
