138 THE VOYAGE OF H.M.S. CHALLENGER. 



The branchiae in this species are of the normal character, but there is no evidence of 

 even a rudimentary mastigobranchial lash attached to the first pair of gnathopoda, as we 

 see in Pentacheles euthrix ; in the second pair it is in a more rudimentary condition 

 than in that species. The mastigobranchiae attached to the several pairs of pereiopoda 

 are of great tenuity, and shorter than the podobranchise. 



Polycheles helleri, Spence Bate (PI. XIV. fig. 2 ; PI. XV. fig. 1). 



Polycheles lielleri, Sp. B., Ann. and Mag. Nat. Hist., ser. 5, vol. ii. p. 276, 1878. 

 Pentacheles helleri, on pi. xv. 



Carapace not broader than the first and second somites of the pleon, lateral margins 

 subparallel, anterior division armed with seven teeth, median with four, and posterior 

 with four or five well-developed teeth near the anterior extremity, from which they 

 gradually decrease in size posteriorly; dorsal central ridge armed with tw T o rostral teeth 

 directed upwards on the anterior margin, which, with the series in the median line, may 

 for convenience be formulated, commencing anteriorly, as 2-1-1-2-1, fossa 2-2-2. 



The pleon (PI. XIV. fig. 2p) is carinated on the five anterior somites, the anterior 

 margin of the crest of each somite culminating in an anteriorly-directed point. 



Habitat. — Station 170, near the Kermadec Islands, north of New Zealand, July 14, 

 1874; lat. 29° 55' S., long. 178° 14' W.; depth, 520 fathoms; bottom, volcanic mud; 

 bottom temperature, 43°. One specimen. 



Length, about 36 mm. (1*5 in.). 



Station 218, north of New Guinea, March 1, 1875 ; lat. 2° 33' S., long. 144° 4' E.; 

 depth, 1070 fathoms ; bottom, blue mud; bottom temperature, 36° - 4. One specimen. 



Length, 50 mm. (2 in.). 



This species is rather more slender than Polycheles baccata, and is readily distinguish- 

 able in having a double rostral tooth arising from the anterior margin of the carapace, 

 and none from the metope between the first pair of antennae ; the anterior margin of the 

 carapace is smooth and recedes gradually to the orbit, which forms a rather large notch 

 in the dorsal surface of the carapace, and thence it advances obliquely outwards to a 

 sharp tooth that forms the latero-anterior angle of the carapace. The lateral margin is 

 furnished with six teeth on one side, and seven on the other in the anterior division ; 

 three on the median ; on the posterior, or that portion of the margin of the carapace that 

 lies behind the cervical fissure, there are two or three tolerably conspicuous teeth situated 

 anteriorly, and so also near the posterior margin, but in the space between these two 

 points, the teeth are only represented by small notches or are entirely wanting. 



The median line of the carapace is armed with a series of distal teeth, on the anterior 

 margin are two rostral teeth that stand obliquely upwards and forwards, behind which in 



