104 



MR. E. C. BOTJSFIELD ON THE 



corpuscles. First five segments destitute of dorsal setse ; the sixth 

 and following haviag Loth dorsal and ventral setse, the latter 

 hooked, the former straight, and one forked bristle in each bundle. 

 Contractile loops in the sixth and some following segments, one 

 in each. 



a. Without secondary branchiae. 



1. Deeo latissima, Bousfield (5). PL IV. fig. 8. 

 Segments 30-40. Contractile loops 4. The branchial area 



with entire margin, well developed, width in full expansion 

 exceeding length, capable of complete eversion, then becoming 

 convex. Branchise long, well developed, piano-cylindrical. 



2. Deeo Pereieri, Bousfield. PI. IV. figs. 4-7. 

 Dero obtusa, Perrier (22). 



Segments 25-35. Contractile loops 3-5. Branchial area with 

 entire margin, trefoil-shaped in full expansion. Branchial pro- 

 cesses well developed, cylindrical, the posterior pair longer than 

 the anterior. 



3. Dero obtusa, D'Udehem (6). PL III. figs. 1-3. 

 Segments 45-50. Contractile loops usually 4 (4-6). The 



branchial area somewhat irregular, and apt to be unsymmetrical. 

 Branchise rather short, foliate ; the posterior margin nearly 

 straight, the anterior curving outward at the middle. A dis- 

 tiuct dorsal lip, divided from the alar portions of the area by 

 a deep groove on each side. 



This species shows the first trace of the modification which 

 leads to the formation of supplementary branchial processes in 

 the distinct demarcation of the dorsal lip, at the angles of which 

 they are borne by those species which possess them. 



4. Deeo Mulleri, sp. nov. PL IV. figs. 9, 10. 



Segments 70-95. Contractile loops usually 7 (6-8). The- 

 branchial area with separate dorsal lip. Branchial processes 

 oblong, quadrangular, the attached border the longest, superior 

 angles rounded. 



The largest of all known species. Furnished to the writer by 

 Mr. Bolton. Chains of two zooids frequently consist of 130-140 

 segments, and measure nearly an inch in length. Branchial area 

 disproportionately small. 



