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THE VOYAGE OF H.M.S. CHALLENGER. 
interior orbital hiatus by a process of its extero-distal angle, but this process is not in 
contact with the inferior margin of the front. The chelipedes and ambulatory legs 
present nothing remarkable; the merus-joints of the fifth legs are armed with a spine 
placed near the distal extremity of the inferior margin. 
Cronius is connected with Goniosoma through such species as Goniosoma erythro- 
dactylum, which has fewer antero-lateral marginal teeth, but one or two rudimentary as 
in Cronius. 
The following species are included in Cronius : — 
Cronius ruber (Lamarck) = Amphitrite edivardsii, Lockington. Gulf of Mexico ; 
West Indies ; Vera Cruz ; Brazil ; Panama (East Coast) ; Mazatian. 
Cronius milleri (A. Milne Edwards). Cape Verde Islands (St. Vincent) ; Sene- 
gambia, Goree Island, 9 to 15 fathoms. 
Cronius bispinosus, n. sp. Brazil, Bahia. 
Cronius bispinosus, n. sp. (PI. XV. fig. 2). 
I propose to designate thus a small species which is distinguished from all its congeners 
by having but two spines on the palm of the chelipedes, and from all, except perhaps 
Cronius edwardsii (Lockington), by having the third frontal tooth in the adult wholly 
confluent with and indistinguishable from the external frontal (or inner orbital tooth). 
In nearly all other characters this species closely resembles the well-known Cronius 
ruber , l but it is further distinguished by the unarmed merus -joint of the fifth or swimming 
legs from that species. The carapace is shaped nearly as in Cronius ruber; it is 
moderately convex, pubescent, and has straight, transverse, smooth lines or low ridges on 
the gastric and cardiac regions, and a similar but curved ridge passing inwards along the 
front of the branchial regions from the lateral epibranchial spine. The frontal lobes are 
somewhat broader, less prominent and more obtuse than in Cronius ruber, the median 
ones are separated from one another by a much shallower interspace, the next on each 
side are as broad as long, and subtruncated or but slightly rounded at the distal extremity, 
the third, as already stated, are wholly confluent with the outer teeth, and they form 
together a broad truncated lobe. The antero-lateral margins are armed with eight 
alternately larger and smaller spines, as in Cronius ruber, but the first two teeth 
are somewhat blunter and less spiniform than in that species ; the ninth (or lateral 
epibranchial spine) is distinctly longer than any of the preceding. As in Cronius 
ruber, the basal antennal joint terminates in a short spine or tooth. The outer 
maxillipedes closely resemble those of that species. The chelipedes are subequal ; the 
merus or arm has but four spines on its anterior margin ; the small spines which usually 
exist at the distal extremity of both the anterior and posterior margins of the arm in 
1 Vide A. Milne Edwards, Crust, in Miss. Sci. au Mexique, pt. 5, p. 232, 1879. 
