ONUPHIS PACHYTMEMA. 279 



Locality. Off :Mexico: Sta. 3415 (lat. 14° 46' N., long. 98° 40' W.). 

 Depth 1,879 fms. Bottom of gi-een mud. Bottom temp. 36° F. 10 April, 

 1891. Several specimens. 



This species has a number of sinularities to 0. nehulosa Moore secured in 

 Monterey Bay in much shallower water (65-71 fms.). In the latter species 

 the gills begin similarly on somite VIII (or IX) and are largely simple, with 

 bifilamentous ones frequent and a maximum number of fom* filaments; however, 

 more of the gills seem to be divided and the longest of them just reach the mid- 

 dorsal Une instead of passing much beyond it. The anterior parapodia are 

 longer. The postsetal process of the parapodia undergoes reduction much more 

 gradually. The anterior crochets differ in ha^'ing two accessory teeth instead 

 of but one and noticeably in lacking the conspicuous prolongation to the guards. 

 The posterior crochets differ perceptibly in having the lower teeth directed more 

 nearly at right angles to the axis and making a decidedly larger angle with the 

 apical tooth. The ceratophores of the dorsal tentacles differ in being distinctly 

 quadriannulate. The maxillae are very sinular in general appearance; the 

 teeth of maxillae II are more numerous (ten instead of eight), and the left and 

 right maxillae III have six and eight teeth respectively instead of four and 

 seven in litabranchia. 



OnUPHIS PACHYTMEMA, Sp. nOV.^ 



Plate 48, fig. 5-11; Plate 49, fig. 1-8; Plate 50, fig. 1-6. 



The_ general color is light brown, with a pale ventral neural stripe showing 

 enlargements corresponding to the ganglia and also a fight median longitudinal 

 dorsal stripe excepting anteriorly; below each parapodium is a swollen, whitish 

 glandular area; the cirri are pale. 



A complete specimen in one piece was not secured. Tliree fragments of 

 one specimen had a total of eiglity-five somites and together measured 85 mm., 

 the maximum width being 3 mm. A second specimen, also in three fragments, 

 had also eighty-five somites, or very close to that number, a total length of 98 mm. 

 and a maximum width of 3.25 mm. The body seems thus to be proportionately 

 stout and rather short, widest in the middle region, where the width is nearly 

 uniform, and narrowing at the ends, less conspicuously so at the caudal. The 

 body is low, being compressed dorsoventrally. 



The prostomium is somewhat hemispherical and is circular in outUne in 



' naxi'i, coarse, riirja, segment. 



