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



common to many genera, but absent in this one, and is more nearly associated with the 

 ophthalmus. 



The first pair of antennae has a short and stout peduncle, the first joint being 

 excavate on the upper surface and furnished on the outer with a short pointed stylocerite; 

 the second and third joints are cylindrical and terminally support two flagella, one of 

 which is slender and the other robust, to a greater degree apparently in both sexes than 

 is common. The peduncle is short, and situated close beneath the ophthalmopoda, has 

 the first joint excavate or hollowed for the greater freedom of its movement ; on the 

 outer side the stylocerite exists as a thickened mass, pointed somewhat obtusely at the 

 extremity, the outer margin being a vertical wall. 



The second pair of antennae carries a scaphocerite that is broad, tapering, and 

 membranous, of considerable tenuity, and strengthened on the outer side by a ridge that 

 terminates in a small tooth near the distal extremity ; the peduncle has two very thick 

 joints beyond the articulation of the scaphocerite. The length of the flagellum is nearly 

 equal to half that of the animal. 



The mandibles approximate in form to those of Notostomus in having a large psalis- 

 toma with a serrate margin continuous with the molar process, which is small, and carries 

 a three-jointed synaphipod, the terminal joint of which is spatuliform. 



The other oral appendages also resemble those of Notostomus, differing from them, 

 apparently, only to a slight degree. 



The gnathopoda also to a considerable extent resemble those of Notostomus. The 

 first pair is subpediform and seven-jointed ; the propodos and dactylos are broad, flat, 

 and reflexed ; the basis carries a long ecphysis, and the coxa supports a mastigobranchial 

 plate, near to which, but separated from it, is a small arthrobranchial plume. 



The second pair is pediform and five-jointed, the ischium and meros, and the propodos 

 and dactjdos being probably united ; the ischio-meral joint is longitudinally triangulate 

 and curved to afford room for the oral organs ; the basis probably carries a rudimentary 

 mastigobranchia, an arthrobranchial plume and an ecphysis, although I have not been 

 able to determine it in the partially damaged specimen. 



The first two pairs of pereiopoda are slender and chelate, the propodos not being 

 enlarged; they are similar in form and subequal in size, the anterior being somewhat the 

 smaller, and have the meros compressed, and each is furnished with a basecphysis, a rudi- 

 mentary mastigobranchia, and two arthrobranchial plumes. The three succeeding pairs 

 have the meros long and transversely flattened, the carpos short and the meros long and 

 cylindrical, and the dactylos long and styliform except in the posterior pair, which is 

 short and has the propodos furnished posteriorly with short stiff spinules ; all carry a long 

 basecphysis. 



The first pair of pleopoda has the inner ramus membranous, and almost rudimentary 

 iu some species, whereas in others, as in Hymenodora glauca, it is larger and leaf-like, 



