Boone, Crustacea, Cruise of "Alva," 1931 51 



Technical description: This species is most closely related to 

 Lissocarcinus orbicularis Dana,* from which it differs in the following 

 essentials : 



(a) The frontal margin is not protuberant beyond the preorbital 

 angle and is sharply defined from the orbital angle which is acute, 

 triangulate. 



(b) The anterolateral margin has only one incision, that separat- 

 ing the postorbital angle from the rounded first anterolateral tooth. 

 The dorsal surface of the carapace has a recurved sulcus behind the 

 orbit and across the hepatic and frontal regions not shown in 

 L. orhicularis Dana. 



(c) The antennal flagellum is quite long. 



(d) The cheliped differs in that the carpus has three longitudinal 

 carinae; the palm is devoid of the tubercle adjacent to the carpal 

 joint ; the upper surface of the palm has two longitudinal carinae, but 

 these do not terminate in teeth, they are tapered and rounded distally ; 

 the outer surface of the palm has one longitudinal carina which is 

 also devoid of a tooth distally. The palm is longer in proportion to 

 the carpus than that of L. orbicularis as figured by Dana, and the 

 fingers, while similar, are shorter in relation to the palm. 



(e) The first to third pairs of ambulatories inclusive have the 

 dactyli shorter in relation to their respective propodi and more curved, 

 hooklike, as in Caphyra. However, the presence of natatory fifth legs 

 is distinctive. 



The carapace is subcircular, 7.5 mm. wide, 6.5 mm. long, the inter- 

 orbital space 4.8 mm. wide, the frontal margin is wide, thin, laminate, 

 slightly incised in the median line and set apart at the blunted outer 

 angle by a distinct notch from the preorbital angle, which is a small 

 triangle. The orbital margin is cut by two closed sinuses. The antero- 

 lateral margin is cut by a closed incision indicating a single closed 

 tooth but not breaking the marginal contour. The margin is convex, 

 laminate, continuous with the postlateral margin which is also convex, 

 except where it is decidedly concavely excavate above the bases of the 

 fifth pair of legs. The posterior margin is short, concavely excavate 

 and emphasized by a flat carina. The dorsal surface of the carapace 

 is convex, smooth, the regions not delineated, except for a very faint 

 urogastric line. There is a curved, depressed sulcus behind each orbit 



• Lissocarcimis orbicularis Dana, U. S. Explor. Exped., vol. XIII, pt. I, p. 

 288, Atlas, pi. 18, fig. la, 1852. This species was collected in the coral reefs of 

 Ovalu, Feejee Archipelago. 



