156 MR. F. E. BEDDARD ON A [Feb. 15, 



body, and there is therefore no prostomium ; in this character 

 Thamnodrilus agrees with UrochcBta^ and Biachcefa'. It is a little 

 difficult to distinguish the anterior segments of the body ; the 

 buccal segment is divided externally by a very well-marked furrow, 

 which appears to mark the line of division between two really 

 distinct somites. A consideration of the number of the nephridia 

 (see p. 160) leads me to infer that the divisional furrow does not 

 imply a division into somites : furthermore (see figs. 1 and 2) each of 

 the two anterior rings is divided on each side by a longitudinal 

 furrow, which corresponds in position with the dorsal pair of setae 

 in the following segments ; tlie presence of this furrow is perhaps 

 an additional argument in favour of regarding them as parts of the 

 same somite. 



From the first segment to about the 8th, the breadth of the 

 segments gradually increases ; the longitudinal diameter of the 

 segments also gradually increases up to the 8th or 9th, after which 

 they become distinctly narrower. 



The segments of the clitetlutn are perfectly distinct, and are eleven 

 in number. The clitellum commences with the 15th segment and 

 terminates npon the 25th ; very generally a trace of glandular 

 modification is to be found upon the 14th and 26th segments. 



The clitellum of Thamnodrilus is therefore nearly coextensive with 

 that of Vrobenus, Urochaeta, Titanus, and Aniens. 



As in the former genus, the clitellum is not developed upon the 

 ventral side of the body, but the extent of the area left free from 

 glandular substance varies ; in the anterior part of the clitellum, 

 as far back as segment 19, the ventral pair of setae as nearly as 

 possible mark the boundary between the glandular and non-glandular 

 portion of the integument ; from the 20th segment to the end of 

 the clitellum there is a space left between the glandular part of the 

 integument and the setae. This is illustrated in the accompanying 

 drawing (woodcut, fig. 2). 



The set(B are disposed in pairs ; the distance separating the 

 ventral pairs is 2"2 mm. in the clitellar region, the distance between 

 the ventral and dorsal pair is 5'5 mm., while the dorsal pairs are 

 separated by an interval of 12"5 mm. The setae are not remarkable 

 in shape except npon the clitellum ; here they are modified and 

 acquire the form illustrated in the drawing (woodcut, fig. .3) ; these 

 peculiarly modified setae are apparently found throughout the 

 clitellum (I have also found them in segments immediately anterior), 

 where they replace both the dorsal and ventral pairs. The accom- 

 panying figure renders any minute description of these setae unneces- 

 sary, and will serve to show how exactly they resemble the clitellar 

 setae of Urochceta ; in this genus Perrier has recorded ■* the modi- 

 fication of the ventral pair of setae on the 20th segment ; and ITorst 

 has stated ■* that in another species the ventral setae of four of the 



^ Perrier, Arch, cle Zool. Exper. t. iii. 



^ Benham, Quart. Journ. Mier. Sei. 1886. 



3 Arch. A. Zool. Exper. t. iii. (1874) p. 399, pi. xvii. iig. 52. 



* Midden Sumatra, Vermes, p. 8. 



