NATURAL HTSTORT OP THE GENUS DERO. 



105 



l3. With secondary branclnaD. 



5. Dero limosa, Leidi/ (15). PL V. figs. 11-16. 

 Dero philippinensis, Semper (26). 



Segments 55-60. Contractile loops 5, the last much the 

 smallest. The branchial area with dorsal lip, each angle bearing 

 a secondary branchia, short, cylindrical, and contaiuing a loop of 

 blood-vessels. Branchial processes as in D. obtusa, but longer 

 and narrower. 



The foregoing species appears to me, for reasons already 

 stated, to be identical with Prof. Leidy's ; and there is no 

 difference which cannot be explained on the grounds laid down 

 (p. 100). Should the species under notice hereafter prove to 

 be distinct from Prof. Leidy's, it will stand as new, unless 

 indeed it be the same as Prof. Semper's D. philippinensis, as on 

 the same considerations seems probable ; though the latter may 

 possibly be identical with the species next to be described, a point 

 which cannot be settled in the absence of a figure of Prof. Semper's 

 worm. 



6. Dero acuta, JBousJield (5). 



Characters nearly as in D. limosa; but the branchiae much 

 longer, obovate in form, wdth pointed apices ; length about 4 or 

 5 times the greatest breadth. 



Only two examples of this species have come under my notice 

 from the localities already mentioned (p. 103). A careful search 

 during the present season has been unsuccessful ; so that no 

 figure can be given; but there will be no difficulty in recognizing 

 the worm from the description above. 



y. With secondary branchiae and palpi. 



7. Deeo ruRCATA, Oken (20). PI. V. figs. 17, 18. 



Das geschmeidige Wasserschliinglein mit zwey G-abelspizen, 

 Rdsel (24). — Dero palpigera, Grebincky. — Dero Eodriguezii, 

 Semper (26). 



Segments 35. The branchial area more funnel-shaped than in 

 the other forms ; the dorsal lip not divided off, but bearing sup- 

 plementary branchiae at its junction Mdth the alae. The integu- 

 meutal layer at the tip of the branchial area prolonged into two 

 palpi of varying length, non-ciliated, extra-vascular. Branchiae 

 nearly cylindrical ; contractile loops five. The first dorsal bristle- 

 bundles in the fifth segment. 



