SHRIMPS OF THE GENUS BETAEUS — HART 451 



shell, but it soon returns to its shelter. More frequently it may be seen on the 

 upper surface of the frilly mantle edge of its host. At the least disturbance it 

 hastens beneath the mantle and the abalone closes down over it in what resembles 

 a protective manner. 



In a letter, Mrs. G. E. MacGinitie states: 



When the abalone diver brought in so many live B. harfordi we dumped about 

 20 of them in an aquarium with two H. corrugaia. The next morning practically 

 all of them had found a niche somewhere in the two abalones. But they did 

 not all stay with the abalones very long. One per abalone is apparently normal, 

 and soon the others were elsewhere. Six or more took refuge in the niches of the 

 egg case of the horned shark. Another snuggled next to the third abalone in the 

 aquarium — a specimen about an inch long, and the shrimp was at least as long 

 as the "host." 



Ovigerous females have been taken in March, April, May, Septem- 

 ber, and December. Mrs. MacGinitie reports that the eggs, when 

 freshly laid, are nearly opaque and a pale yellowish green, becoming 

 more transparent with development. 



Betaeus macginitieae, new species 



Figures 48, 49, 55, 62-64, 75, 76 



Alpheus aequalis Holmes, 1900, p. 189 (part, specimens found on sea urchins). 

 Betaeus harfordi MacGinitie and MacGinitie, 1949, p. 279 (part, purple ones with 

 sea urchins). 



Female. — Carapace laterally compressed but without carina; 

 smooth, naked. Front (fig. 48) produced to form hood, which is 

 curved slightly anteriorly but without emargination. Lateral margin 

 (fig. 49) faintly curved, closely adhered around base of antenna with- 

 out distinct anterolateral angle. Width of carapace increasing 

 rapidly to base of maxilliped, then decreasing slightly to form curved 

 lateral margin. Posterolateral junction rounded; posterior margin 

 nearly straight ventral to junction of cardiac notch. 



Abdomen smoothly rounded. Posterior margins of all pleura 

 rounded but that of fifth somewhat acute. No surface setae and only 

 pleura of first segment margined ventrally with plumose setae. 



Telson (fig. 62) flattened, longer than sixth segment. About twice 

 as wide proximally as distally. Two pairs of movable spines dorsally. 

 Posterior margin curved, with pair of small spines (outer smaller) 

 externally, and long plumose setae. 



Eye oval, on short eyestalk with small tooth, 



Antennule with stylocerite narrow, reaching to last quarter of 

 second segment of peduncle. Peduncle with middle segment nearly 

 twice as long as either first or third; almost bare of setae. Peduncle 

 about /^ length of carapace. Ventrally near distal margin of first 

 segment a stout laterally compressed tooth. Inner flagellum stout, 

 elongate. Fused part of outer flagella stout but free tips short. 



