SHRIMPS OF THE GENUS BETAEUS — ^HART 435 



Betaeus harrimani Rathbun 



Figures 1-26, 29-31, 37-39; Plate 1 



Betaeus harrimani Rathbun, 1904, pp. 108-110, fig. 49 (type locality, Sitka, 

 Alaska; holotype female, USNM 25692).— Banner, 1953, p. 5. 



Female. — Carapace laterally compressed but without carina. 

 Smooth, with minute setae sparsely scattered except where concen- 

 trated ventral to hepatic region, where they form a pubesence (seen 

 best in cast skins of large individuals). Longer setae under front 

 and along posterior margin. Front (fig. 17) slightly curved and 

 depressed anteriorly. Anterior margin (fig. 18) with two shallow 

 sinuses. No distinct anterolateral angle. Width of carapace in- 

 creases to midlateral point and then decreases slightly with faint 

 undulations on margin. Lateral margin joins posterior in smooth 

 curve. Posterior margin angles in sharply to deep cardiac notch. 



Abdomen (fig. 1) smoothly rounded with posteroventral margin 

 of pleura of first to third segments rounded, those of fourth and fifth 

 segments angled. First and fifth pleura margined with setae ven- 

 trally. Minute setae on smooth surface. 



Telson (fig. 26) longer than sixth abdominal segment, much longer 

 than wide, outer margins curved. Two pairs of movable spines on 

 dorsal surface, two spines at each posterolateral angle; outer ones 

 small. Posterior margin deeply curved, plumose setae long. 



Eye round with short, sharp-pointed tooth on each stout eyestalk 

 medially. 



Antennule with stylocerite broad at base; outer margin slightly 

 convex, inner concave, tip reaching almost to end of second segment 

 of peduncle. First segment of peduncle with sharp compressed 

 tooth ventrally (fig. 2). Second joint usually longer than third. 

 Outer flagellum with sensory part fused except for about three seg- 

 ments that are free from slender terminal flagellum. 



Antenna with peduncle slightly longer than that of antennule. 

 Distal margin of basis produced into sharp-pointed flat tooth ventrally. 

 Scale (fig. 19) broad: wide spine exceeding blade, separated from 

 it by short slit distally, outer margin straight. Tip reaching past 

 middle of last segment of antennular peduncle. Flagellum longer 

 than carapace, ovoid in cross section. 



Mandibles, maxillules, maxillae, first and second maxillipeds 

 (figs. 3-7) similar to those of Betaeus truncatus Dana, as described by 

 Holthuis (1952), but appearing more setose, as illustrated. 



Third maxilliped (fig. 8) reaching to end of antennal peduncle. 

 Ischiomeropodite flattened, twisted. Exopodite longer than ischio- 

 meropodite but narrow, fragile-looking, with soft plumose hairs 

 distally and striations on cuticle that can be observed in cast skins. 



