REPORT ON THE CRUSTACEA MACRURA. 425 



the Atlantic, the differences being so slight that they would not justify its separate notice 

 from Sergcstes semiarmis, but for the distance between their habitats. 



This specimen has the scaphocerite long and narrow, the sides parallel, the outer 

 smooth and armed with a long tooth at a point equal to its length from the 

 extremity. 



The first pair of pereiopoda is slender and exhibits no trace of a prehensile apparatus. 

 The chela of the second pair of pereiopoda is minute and rudimentary, the pollex 

 particularly so. The fourth and fifth pairs of pereiopoda are minute and bud-like, as if 

 they were only commencing to be developed. 



The sixth somite of the pleon terminates dorsally in a prominent tooth instead of in 

 a blunt point as in the typical specimen, and the telson terminates in a minutely-forked 

 extremity. 



These two forms are, I believe, early stages of a much larger specimen, but their 

 matured shape compels us to accept them as specific forms until the life-history of the 

 species be made clear. 



Sergestes IseviventraUs, n. sp. (PI. LXVIL.fig. 3). 



Carapace more than one-third the length of the animal. Rostrum as long as the 

 ophthalmopod, armed with a tooth immediately over the frontal margin. 



Pleon armed with a tooth at the posterior dorsal surface of each somite, those on the 

 anterior three somites being vertical, and on the posterior three directed backwards. 

 The median ventral line of the pleon is free from spinous processes. 



Telson about half the length of the sixth somite. 



Ophthalmopoda clavate, not longer than the rostrum, robust ; the ophthalmus but 

 little larger than the diameter of the distal portion of the stalk. 



The first pair of antennae has the first joint of the peduncle rather longer than the 

 ophthalmopod ; second and third short, subequal, and together about the same length as 

 the first. 



The second pair of antennas has the terminal joint of the peduncle reaching nearly 

 to the extremity of the ophthalmopod, and carries a scaphocerite that reaches as far as 

 the distal extremity of the peduncle of the first pair of antennas. 



The mandible is at a considerable distance from the antenna?, and is, I believe, 

 furnished with a small two-jointed synaphipod, although in the present condition of the 

 mounted specimen I could not positively determine it. 



The first pair of gnathopoda terminates in a short spatuliform dactylos. 



The second pair is long and slender, having the coxa larger than in any of the other 

 appendages of the pereion. 



The first pair of pereiopoda is slender and about half the length of the second 



(ZOOL. CHALL. EXP. PART LII. 1887.) Fff 54 



