REPORT ON THE CRUSTACEA MACRURA. 431 



the dactyloa is wanting. The posterior margin of the several joints are anteriorly 

 smooth, posteriorly semiserrate, and fringed with very long delicately ciliated hairs. 

 The fifth pair is broken off at the coxa. 



The first two pairs of pleopoda are long and rather powerful organs ; the first is 

 single and smooth, as in females, and the second is two-branched. 



Length of part preserved 18 mm., probable length of the entire animal 24 mm. 

 (0-98 in.). 



Sergestes ventridentatus, n. sp. 



Carapace one-third the length of the animal not including telson nor rostrum. 

 Rostrum short, sharp, horizontal, and armed with a small tooth on the dorsal surface 

 anterior to the frontal margin. 



Five anterior somites of the pleon subequal and dorsally smooth ; three anterior 

 ventrally produced in the median line to a plate that is armed with a strong and sharp 

 tooth ; the two posterior lobed and unarmed. Sixth somite equal in length to the two 

 preceding combined, but narrower and produced to a point only at the posterior dorsal 

 angle. Telson one-third the length of the sixth somite, anterior portion deep at the 

 margins, posterior suddenly narrowed. 



Ophthalmopoda rather more than half the length of the carapace, fungiform, stalk 

 suddenly narrowed, ophthalmus broad. 



First pair of antennae having the first joint of the peduncle widened at the base to 

 receive the otocyst, but not' armed with a tooth on the outer margin. The three joints 

 are subequal in length and the first two reach as far as the distal extremity of the 

 ophthalmopod ; the flagellum is slender and as long as the peduncle, the secondary 

 appendage is merely a single-jointed, bud-like organ. 



The second pair of antenna? has the scaphocerite long and narrow, reaching to 

 the extremity of the peduncle of the first pair, and subapically armed with a small acute 

 tooth. The terminal joint of the peduncle reaches to half the length of the 

 ophthalmopod, but the flagellum is lost. 



The first pair of gnathopoda appears to have the terminal joint shorter and more 

 discoid than usual, and much narrower than the preceding joint. 



The second pair is long and powerful, reaching considerably beyond the distal 

 extremity of the flagellum of the first pair of antenna? ; it has the four basal joints broad 

 and stout, and the two terminal narrow and slender, the extremity being fringed with 

 three fasciculi of hairs on the posterior and distal surfaces. 



The first pair of pereiopoda is furnished with a small hook-like process on the 

 anterior surface at the base of the ischium. The second pair of pereiopoda is not fully 

 chelate, but only rudimentarily so ; while the ischium is armed on the posterior margin 



