SHRIMPS OF THE GENUS BETAEUS — HART 439 



bristles. Median to these another tooth. Distal angle of outer 

 margin of proximal part of exopodite a sharp tooth, covering base 

 of stout spine; distal margins rounded, with bristles as well as plumose 

 setae. Bristles dorsally on margin of exopodite, scattered over dorsal 

 surface of endopodite. Exopodite and endopodite nearly equal in 

 size, longer than telson but about same width. 



Male. — Similar to female except that carapace and abdomen 

 slightly more slender, pubescence on carapace thicker, setae on mar- 

 gin of first pleura sparser. Antennular peduncle with middle segment 

 usually distinctly longer than that of females of comparable size. 

 Chelae usually longer than carapace, with same range of variation as 

 females but often somewhat wider, stouter, as are walking legs. 

 Second pleopod (fig. 16) with appendix masculina only shghtly longer 

 than appendix interna, bearing brush of terminal setae. 



Color. — -The living annual (pi. 1) is transparent, except for clu"0- 

 matophores which occur in a distinct pattern. The color consists of 

 small red chromatophores usually surrounded by dark blue spots. 

 The pigmented areas of the carapace are two broad bands on the 

 dorsal part separated by a thin middorsal line that is unpigmented 

 except between the eyes. Two colored patches occur on the carapace 

 at the base of the antennae. In the female the green eggs in the 

 ovary may show through the integument. The abdomen also is 

 pigmented dorsally and, except for the first segment, the segments 

 are clear anteriorly and middorsally but deeply colored in a band 

 posteriorly at the joints. The lateral part of the sixth abdominal 

 segment often is pigmented as is the telson, which, however, has a 

 light streak. There is a fine band of color near the anterior margin 

 of the tergum of the first segment. 



The eyestalks, antennules, and antennae are heavily pigmented. 

 The flagella are reddish. The mouth parts are clear except for the 

 third maxillipeds, which have scattered spots. The chelipeds are well 

 colored, mainly red, but the tips of the claws are clear. The second 

 pair of walking legs is clear, but the rest have scattered red dendritic 

 chromatophores. The uropods are mainly red but the setae are 

 creamy white. 



The color ends in a straight line midlaterally and the ventral parts 

 are quite transparent. The coloration varies with the state of the 

 chromatophores. By day, when the red chromatophores are ex- 

 panded, the animal is reddish or purplish; by night it is distinctly 

 blue. One specimen, after preservation, turned a uniform pale green. 

 The color recorded by Kathbun (1904) is "fight green." 



Size. — Carapace length of smallest ovigerous female 5.5 mm.; 

 largest female 12.5 mm.; males 2.5-13 mm. Length of chela of 

 largest female 10.5 mm.; largest male 14 mm. 



