REPORT ON THE CRUSTACEA MACRURA. 



575 



the propodos is not longer than the dactylos of the larger chela ; the dactylos is much 

 longer than the pollex and curved in the form of a hook. The second pair of 

 pereiopoda is long and slender, and the carpos seven-jointed, the first articulus being as 

 long as the three following ; it terminates in a small chela. 



Telson broad at the base and tapering, rounded at the distal margin, fringed with 

 hairs and dorsally armed with two spines on each side of the median line. 



Length, entire (female), 



„ of carapace, 

 Depth of „ . . 



Length of pleon, 



The males are smaller and less robust. 



-Length, entire (male), 



,, of carapace, 

 Depth of ,, 

 Length of pleon, . 



,, of large chela, 

 Width of ,, „ 

 Length of dactylos of large chela, 



„ of small chela, 



,, of dactylos of small chela, 



,, of pollex of ,, 



33 mm. (1*3 in.). 

 13 „ 

 10 „ 



20 „ 



Habitat. — Station 186, September 8, 1874; lat. 10° 30' S., long. 142° 18' E.; 

 between Cape York and the Arrou Islands ; depth, 8 fathoms ; bottom, coral mud. 

 Six specimens ; four males and two females. Dredged. 



This species may be readily known by the elevated dorsal median ridge, which rises 

 from the apex of the rostrum and continues as a small carina to the posterior extremity 

 of the gastric region, where it is lost. The female is more than one-fourth longer and 

 broader than the male and carries many broadly ovate ova, 1*5 mm. in the longest 

 diameter. 



The ophthalmopoda are observable as semi-movable organs beneath the carapace and 

 a longitudinal ridge corresponds with the outer angle of the first pair of antenna?. The 

 stylocerite is nearly as long as the rostrum and longer than the first joint of the 

 peduncle (c, b). The phymacerite attached to the second pair of antennae terminates in 

 a strong, tooth-like, but not very prominent point. The mandible (d) has a large molar 

 protuberance, a small tooth-like process representing the psalistoma, and a small two- 

 jointed synaphipod, and bears a closer resemblance to the same organ in Spirontocaris 

 than to that in Alpheus. The other oral appendages agree with those of AlpheUs, or 

 when they differ the differences are only such as may be expected in characters of 



