SHRIMPS OF THE GENUS BETAEUS — ^HART 449 



setae. Ischium and merus comprise }^ length of appendage. Large 

 movable spine on merus. Carpus, with minute terminal spines, sub- 

 equal in length to propodus. Propodus armed ventrally with small 

 setae and vestigial spines. Terminal pair larger. Dactylus (fig. 74) 

 short, stout, bifid, but claws masked by two median bands of short 

 stiff bristles. 



Fourth leg similar to third, but all segments except ischium slightly 

 smaller. 



Fifth leg distinctly shorter than fourth. Subequal merus and 

 propodus each longer than carpus. Brush of 4-5 bands of short stiff 

 setae on distal part of propodus. Dactylus similar to that of third 

 and fourth legs. No movable spine on merus. 



First pleopod with round-tipped endopodite, nearly ji length and 

 width of slender exopodite. Second pleopod with subequal slender 

 endopodite and exopodite. Appendix interna straplike, nearly % 

 length of endopodite. 



Uropod (fig. 58) with posterior margin of peduncle produced into 

 two sharp subequal teeth, separated by concave margin with few small 

 setae. Distal angle of proximal part of exopodite a sharp tooth, 

 covering base of short stout spine. Uropods longer than telson. 



Male. — Similar to female except that chelae (fig. 59) are propor- 

 tionately larger, subequal in length to carapace. Appendix masculina 

 with bristles on margin of distal half and on blunt tip; twice as long 

 as appendix interna, nearly as long as endopodite. 



Color. — Dark purple (Lockington, 1878; Holmes, 1900), blue-black 

 (specimen label, E. P. Chace), deep blue (specimen label, W. A. 

 Hilton) and deep blue, occasionally reddish-brown on sides (Mrs. 

 G. E. MacGinitie). 



Size. — Carapace length of smallest ovigerous female 6 mm.; largest 

 female 10.7 mm; males 3.3-8 mm. Length of chela of largest female 

 8.5 mm.; of largest male 8 mm. 



Range. — ^Magdalena Bay, Mexico, to Fort Bragg, Calif, (personal 

 communication, Mr. Keith W. Cox) ; intertidal to depth of 12 fathoms. 

 This is apparently a very elusive shrimp that leaves its host with little 

 provocation, with the residt that, unless precautions are taken to 

 prevent its escape, it may be consistently missed when abalones are 

 collected. UntU Mr. Cox was consulted, no specimens had been 

 recorded in any collections taken north of Santa Monica, even with 

 Mr. D. Montgomery checking approximately 350 specimens of 

 Haliotis from the vicinity of San Luis Obispo. On the other hand, 

 Dr. Howard Teas, on April 4, 1953, collected at El Estero de Punta 

 Banda, Ensenada, Baja California, Mexico, and reported to the Mac- 

 Ginities that about four out of every five Haliotis fulgens had a 

 Betaeus in the mantle cavity. 



093-433—63 3 



