122 PROCEEDINGS OF THE NATIONAL MUSEUM vol.84 



3. Body 40 to 50 mm long; with 70 to 89 segments; poriferous carinae 



very broadly and evenly rounded in outline, hind angles indis- 

 tinct protenta 



Body less than 40 mm long; number of segments less than 70; 

 poriferous carinae not so decidedly rounded, hind angles dis- 

 tinct 4 



4. Gonopods with apex of each erect piece not at all expanded, w^hen 



viewed from side tiburona 



Gonopods with apex of each erect piece conspicuously expanded, 



when viewed from side 5 



5. Gonopods with margin of expanded apex very distinctly and 



irregularly serrate; poriferous carinae decidedly irregular in 



outline saxetana 



Gonopods with margin of expended apex continuous, not serrate; 



poriferous carinae without large irregularities sideralis 



COLACTIS SAXETANA, new species 

 FiGtJBE 16, a, 6; Plate 3, Figukb 2 



Desciiption. — Body slender, 21 to 33 mm long and 1.3 to 1.8 mm 

 broad, composed of 56 to 68 segments ; dorsum slightly depressed, the 

 females more so than the males; males not appreciably more con- 

 stricted behind segment 1 than the females (pi. 3, fig. 2). 



Eye cluster quadrate, with 35 to 50 ocelli in 6 to 9 rows ; sense organ 

 opposite the third row of ocelli. 



Segment 1 with 10 crests, the median pair of crests parallel and 

 crossing the posterior half of the segment; anterior part of the seg- 

 ment, in front of the crests, faintly and sparsely tuberculate and with 

 10 setae arranged in a triarcuate row. 



Transition to the full number of dorsal crests occurs on segment 16. 



Primary crests of the dorsum prominent and only moderately 

 thickened, highest at the posterior margin of the segment; apex 

 uneven, subdentate when viewed from the side, and with a series of 

 quite large, round pits on either side immediately below it. Second- 

 ary crests usually distinct but considerably lower than the primary 

 crests and reaching across the anterior two-thirds or three-fourths of 

 the subsegment; behind the secondary crests the surface between tlie 

 primary crests gradually descends to a slightly lower level. Sides 

 of the secondary crests, the lower sides of the primary crests, and 

 the surface between both classes of crests roughly and irregularly 

 reticulated, appearing almost scabrous. 



Lateral carinae prominently projecting; in outline the margin is 

 roughly rounded to well behind the middle, from where it parallels 

 the side of the body to the right-angled posterior corner (fig. 16, h). 

 Pore located in a relatively small, broadly oval area occupying the 

 median half of the edge of the carinae of all but a few of the anterior 

 and posterior segments; rim surrounding the poriferous impression 

 decidedly thickened, the apex of uneven height and with a row of pits 



