212 PROCEEDINGS OF THE ACADEMY OF [Vol. LXXV 



Uncini in single series, about 65 on X, 45 on XXII. Thoracic 

 uncini (Plate XVll, fig. 23) broadly triangular, with five or four 

 superior teeth. Abdominal (Plate XVll, fig. 24) much smaller and 

 differently shaped, with usually four teeth. All of these uncini on 

 both thoracic and abdominal tori have the teeth, uniserial, except 

 the lowermost pair of acute ones and the uppermost small one 

 which are sometimes subdivided into pairs. 



Stations 4415, off Santa Barbara Island, 302-638 fathoms, green 

 mud; 4457, off Point Pinos Lighthouse, 40 46 fathoms, dark green 

 mud (type). 

 Melinna cristata (Sars) subspecies. heterodonta nov. Plate XVII, fig. 25. 



A complete specimen measures 80 mm. long and 3.5 mm. wade 

 at the anterior end and has 73 segments, 19 of which are thoracic. 



Prostomium nearlj^ twice as wide as long, with a convex, slightly 

 crenulated anterior margin, a transverse sensory ridge, and pair 

 of small lateral pads near its posterior end; middle field slightly 

 elevated for entire length. Tentacles 14 in type, the middle ones 

 stouter. Lips well developed, the upper much plicated, lower flat, 

 smooth and thick. 



Peristomium united to II, which bears ventrally a deep, free 

 fold into which the prostomium may be retracted. The sides of 

 this collar fold rise into wings which continue on to III and IV, 

 sloping obliquely dorsad and on IV forming a somewhat distinct 

 rounded lobe rising freely above the rest of the wing or flange. 

 Just ventrad to the margin of this are borne the three slender 

 linear tufts of setae belonging to somites II, III and IV. Somite 

 V bears a small torus and a dorsal tuft of setae like those on following 

 segments but smaller. Post-branchial denticulated fold rises from 

 posterior region of V and reaches to anterior part of IV, extending 

 across the entire width of the thorax between the setigerous 

 flanges; margin coarsely denticulated with 14, 15 or 16 unequal 

 triangular teeth, the middle ones larger. One small specimen has 

 only 12. 



Gills in general similar to those of M. cristata and M. denticulata 

 but arising from a thick transverse fold on the dorsum of II and 

 III which is limited caudally by the nuchal hooks. The four 

 pairs are arranged in a trapezoidal figure on each side in such a 

 way that the two more anterior pairs are the more widely separated 

 and alternate with the posterior pairs and the two more medial 

 pairs are slightly caudad of the two outer pairs. The anterior 

 innermost pair are strongly united by a transverse fold and the 

 unions of the others, though confined to their bases, are firm and 

 permanent. The gills thus resemble those of M. cristata rather 

 than M. denticulata. They differ considerably in degree of exten- 

 sion, varying in length from much less than three times to more 

 than five times the width of the thorax, and also vary in the length 

 of their basal union. 



