British TuUficida'. Bij Rev. E. Friend. 283 



Brain with a small median process, and a pair of larger pro- 

 cesses behind. The nephridia are typical, with very large upper lip 

 to the anteseptal. Cfflomic corpuscles larger than in M. ruhro- 

 niveus, and not so numerous. Blood system as in the type. Sperm- 

 funnel short, leading into a spermiducal chamber ; opening on the 

 eleventh segment unpaired. An unpaired receptaculum seminis 

 in segment 10, which receives spermatozoa ; no spermatophores 

 seen. 



1904. — Ditlevsen in Zeitschr. wiss. Zool. Ixxvii., pp. 427-8, 

 figs. 25-6. 



The unpaired male pore proclaims this a true Mono2))/lephorus. 

 If the receptacle contains only spermatozoa, we have a close 

 relationship with Bhyacodrihis, which, indeed, it nearly resembles. 



The following are my own notes, made from the study of living 

 material, before I was aware that the species had already been 

 described as above by Ditle\'sen. 



A tiny worm, 6-10 mm. long, and very slender, segments 65. 

 Yellowish brown or straw coloured. Setie usually 2-3 in front, 

 rarely 4, dwindling to 2 or 1 posteriorly. Sette in front with 

 teeth equal, those behind with small upper tooth. On segment 11 

 two sets of setfe only, usually 3 in a set, with unpaired male pore 

 between. No specialized or penial setse. Node of setie near the 

 upper third. Head somewhat pointed ; front segments with a 

 wider and a narrower annulus, as in many other Tubificids. 

 Chloragogen cells begin in fifth segment. Nephridia with small 

 anteseptal, destitute of peritoneal cells ; postseptal very large. 

 Blood system in front segments much simpler than is usual in 

 this family. Brain with a pair of posterior processes, nearly 

 straight behind, concave in front, with strong anterior attachments. 



In the Thames at Kew, and in Lily Pond at Royal Gardens, 

 August 26, 1911. Collected also near the Tower Bridge, Septem- 

 ber 30, 1911, by Mr. C. Todd. None of the specimens in adult 

 stage. 



[3fonopi/lepho7'US tricJiochvtus Ditlevsen, which is also found in 

 England, must be removed from this genus (1) on account of its 

 paired organs, and (2) by reason of its sette. See later under the 

 genus Ilyodrilus.^ 



The genus Telmatodrilus, which is the only other genus at present 

 known in this group, has not hitherto been found in England. 



B. — Forked Setse with Palmate Setae. 



V. Genus Heterochaeta Clap. 



Rightly retained by Beddard ; unfortunately confused by 

 Michaelsen with Fsammorydes. This genus is distinguished from 

 the foregoing by the presence of palmate setse {Schaufelborsten 



X 2 



