DESCRIPTIONS OF GENERA AND SPECIES 299 



is prolofiffed into two moderately/ long processes. Five pairs of contractile hearts. Hah.— 

 Europe; N. America; Philippines. 



BoTJSFiELD (3) insists upon the identity of Leidy's and Sempee's species with a 

 Dero studied and figured by himself. I am a little uncertain whether a species, 

 concerning which I gave a few anatomical details a year or two since, and which 

 I have already referred to as living inside the dead stems of water plants, is also 

 identical. If so, there are six pairs of hearts and not five, and the first of these 

 give off a branch on either side running forward. The hearts are in segments vi-xi, 

 and those of vii, viii, ix are stouter than the rest. I regard D. acvia of Bousfield 

 as merely a variety of the above; the branchiae are said to be longer. In this 

 SxiEEEN agrees. 



(3) Dero furcata, Oken. 



D. furcata, Oken, Lehrb. d. Naturg. iii, Pt. i, 1815, p. 363. 

 ? D. palpigera, Grbbnitzky, Zapiski novoross. Obstch. Est. 1873, P* *^8. 

 ? D. rodriguezii, Semper, Arb. Zool. Zoot. Wiirzb. 1877/78, p. 106. 



Definition. Number of segments 35. Dorsal setae bundles commence in the fifth segment. 

 Body ends in two long processes, and there are also a pair of supplementary branchiae 

 at sides. Five pairs of contractile hearts. Hob. — Europe ; Trinidad 



This species was obtained by Bousfield from the inside of dead stems in water 

 from the Royal Botanic Gardens, Regent's Park, by Sempeb from Minorca; I have 

 received apparently the same species from Eastern tropical Africa. Bousfield, after 

 remarking that 'D. rodriguezii is undoubtedly the same as the A. vagus of Leidy, 

 D. furcata of Oken, and D. palpigera of Geebnitzky,' omits the second name in 

 his list of synonyms. Sempee's figure (1, Taf. iv. fig. J5) represents the supple- 

 mentary branchiae as springing from the anal area like the other branchiae. 

 Stieben received this species from Trinidad. 



(4) Dero perrieri, Bousfield. 



D. perrieri, Bousfield, Rep. Brit. Ass. 1885, p. 1098. 

 D. obtusa, Pebeiee, Arch. Zool. Exp. 1873, p. 6^. 



Definition. Number of segments, 2i5- Branchial area with entire margin. Hearts three to 

 five pairs. Hob.— Europe. 



Bousfield is, no doubt, right in distinguishing between B. obtusa of d'Udekem 

 and B. obtusa of Peeeieb. The entire margin of the gill-area in Peeeier's species 



Qq 2 



