Boone, Crustacea, Cruises of ''Eagle" and "Ara," 1921-28 217 



Color : This species possesses in marked degree the power of rap- 

 idly changing its color in mimicry of that of its surroundings, a fact 

 which explains the various colors ascribed to it by different authors. 

 Dr. Verrill states : ' * Color — pepper and salt, pale yellow, straw color 

 or yellowish white, imitating the color of the beaches." This con- 

 forms to the present writer's observations made on a number of speci- 

 mens in the West Indies and southern Florida. Occasional specimens 

 taken from the spray were pale seafoam green. 



Technical description: Carapace subrectangular, interorbital 

 space 5 mm. wide; upper border of orbit sinuous, produced to a 

 rounded point at the distal end of the eyestalk, thence arcuate to the 

 acute anterolateral angle; the frontal border is beaded or finely ser- 

 rate ; the lateral borders are slightly bowed anteriorly, but somewhat 

 convergent posteriorly ; below this convergent region the vaulted side- 

 walls of the carapace show in a dorsal view ; the posterior margin is 

 slightly sinuous at the ends but approximately subparallel to the an- 

 terior margin. The anterior part of the cervical groove, the meso- 

 gastric depressions, the urogastric and anterior cardiac regions are 

 clearly delineated. 



The orbit is very large and consists of two chambers; the lower 

 consists of a border which has a triangular sinus below the outer angle, 

 a notch midway and there is a short, triangular tooth near the base of 

 the eyestalk. The eyestalk is very short, exceedingly flexible at the 

 hinge and produced in a tongue-like projection on the upper surface 

 of the cornea. The cornea is very large, shining black, convex distally. 



The antennulae have only the basal joint visible ; this is cylindrical, 

 tapering distally, and is closely appressed in the space below the eye 

 and adjacent to the produced frontal border. The basal joint is much 

 enlarged and modified as an auditory organ. 



The antennae are rudimentary ; the first and second joints are small, 

 fixed; the third joint is nearly as long as the first two, somewhat di- 

 lated distally ; the flagellum consists of twelve tapering rings, of which 

 the proximal two are much larger than the rest. 



The external maxilliped has the exognath exceedingly narrow and 

 tapering, reaching only to the base of the merus; the ischium of the 

 endognath is rectangular, a third longer than broad ; the merus is half 

 the length of the ischium but much narrower distally, both the ischium 

 and merus are transversed medially by a broad, shallow, longitudinal 

 groove ; the palp arises from the outer distal angle of the merus ; the 



